diff --git a/errs/error.go b/errs/error.go
index 2730943..f6a6bfb 100644
--- a/errs/error.go
+++ b/errs/error.go
@@ -3,21 +3,67 @@ package errs
 import (
 	"encoding/json"
 	"fmt"
+	"strconv"
 )
 
 // Error returns the string representation of the error and satisfies the error interface.
 func (f *Failure) Error() string {
-	return f.RuntimeErr.Error()
+	if f != nil && f.runtimeErr != nil {
+		return f.runtimeErr.Error()
+	}
+
+	return ""
 }
 
 // ApiError returns formatted string representation of the API error
 func (f *Failure) ApiError() string {
-	return fmt.Sprintf("%+v", f.ApiErr)
+	if f != nil && f.apiErr != "" {
+		return fmt.Sprintf("%+v", f.apiErr)
+	}
+
+	return ""
 }
 
 // ApiErrors returns array of formatted strings that represents API errors
-func (f *Failure) ApiErrors() interface{} {
-	return f.ApiErrs
+func (f *Failure) ApiErrors() map[string]string {
+	if len(f.apiErrs) > 0 {
+		return f.apiErrs
+	}
+
+	return nil
+}
+
+// SetRuntimeError set runtime error value
+func (f *Failure) SetRuntimeError(e error) {
+	f.runtimeErr = e
+}
+
+// SetApiError set api error value
+func (f *Failure) SetApiError(e string) {
+	f.apiErr = e
+}
+
+// SetApiErrors set api errors value
+func (f *Failure) SetApiErrors(e map[string]string) {
+	f.apiErrs = e
+}
+
+// ErrorsHandler returns map
+func ErrorsHandler(errs interface{}) map[string]string {
+	m := make(map[string]string)
+
+	switch errs.(type) {
+	case map[string]interface{}:
+		for idx, val := range errs.(map[string]interface{}) {
+			m[idx] = val.(string)
+		}
+	case []interface{}:
+		for idx, val := range errs.([]interface{}) {
+			m[strconv.Itoa(idx)] = val.(string)
+		}
+	}
+
+	return m
 }
 
 // ErrorResponse method
diff --git a/errs/error_test.go b/errs/error_test.go
index 1527c36..20d38d0 100644
--- a/errs/error_test.go
+++ b/errs/error_test.go
@@ -1,45 +1,50 @@
 package errs
 
 import (
+	"reflect"
 	"testing"
 )
 
 func TestFailure_ApiErrorsSlice(t *testing.T) {
 	var err = Failure{}
 	b := []byte(`{"success": false, "errorMsg": "Failed to activate module", "errors": ["Your account has insufficient funds to activate integration module"]}`)
+	expected := map[string]string{
+		"0": "Your account has insufficient funds to activate integration module",
+	}
 
 	resp, e := ErrorResponse(b)
-	err.RuntimeErr = e
-	err.ApiErr = resp.ErrorMsg
+	err.SetRuntimeError(e)
+	err.SetApiError(resp.ErrorMsg)
 
 	if resp.Errors != nil {
-		err.ApiErrs = resp.Errors
+		err.SetApiErrors(ErrorsHandler(resp.Errors))
 	}
 
-	f, ok := resp.Errors.([]interface{})
+	eq := reflect.DeepEqual(expected, err.ApiErrors())
 
-	if !ok {
-		t.Errorf("%+v", f)
+	if eq != true {
+		t.Errorf("%+v", eq)
 	}
-
 }
 
 func TestFailure_ApiErrorsMap(t *testing.T) {
 	var err = Failure{}
 	b := []byte(`{"success": false, "errorMsg": "Failed to activate module", "errors": {"id": "ID must be an integer"}}`)
+	expected := map[string]string{
+		"id": "ID must be an integer",
+	}
 
 	resp, e := ErrorResponse(b)
-	err.RuntimeErr = e
-	err.ApiErr = resp.ErrorMsg
+	err.SetRuntimeError(e)
+	err.SetApiError(resp.ErrorMsg)
 
 	if resp.Errors != nil {
-		err.ApiErrs = resp.Errors
+		err.SetApiErrors(ErrorsHandler(resp.Errors))
 	}
 
-	f, ok := resp.Errors.(map[string]interface{})
+	eq := reflect.DeepEqual(expected, err.ApiErrors())
 
-	if !ok {
-		t.Errorf("%+v", f)
+	if eq != true {
+		t.Errorf("%+v", eq)
 	}
-
 }
diff --git a/errs/interfaces.go b/errs/interfaces.go
index d8bedf1..371eec4 100644
--- a/errs/interfaces.go
+++ b/errs/interfaces.go
@@ -4,5 +4,5 @@ package errs
 type Error interface {
 	error
 	ApiError() string
-	ApiErrors() interface{}
+	ApiErrors() map[string]string
 }
diff --git a/errs/types.go b/errs/types.go
index a2705f2..5af2e43 100644
--- a/errs/types.go
+++ b/errs/types.go
@@ -2,9 +2,9 @@ package errs
 
 // Failure struct implode runtime & api errors
 type Failure struct {
-	RuntimeErr error
-	ApiErr     string
-	ApiErrs    interface{}
+	runtimeErr error
+	apiErr     string
+	apiErrs    map[string]string
 }
 
 // FailureResponse convert json error response into object
diff --git a/v5/client.go b/v5/client.go
index 532fe97..c3364fa 100644
--- a/v5/client.go
+++ b/v5/client.go
@@ -25,10 +25,10 @@ func New(url string, key string) *Client {
 }
 
 // GetRequest implements GET Request
-func (c *Client) GetRequest(urlWithParameters string, versioned ...bool) ([]byte, int, errs.Failure) {
+func (c *Client) GetRequest(urlWithParameters string, versioned ...bool) ([]byte, int, *errs.Failure) {
 	var res []byte
-	var failure errs.Failure
 	var prefix = "/api/v5"
+	failure := &errs.Failure{}
 
 	if len(versioned) > 0 {
 		s := versioned[0]
@@ -40,7 +40,7 @@ func (c *Client) GetRequest(urlWithParameters string, versioned ...bool) ([]byte
 
 	req, err := http.NewRequest("GET", fmt.Sprintf("%s%s%s", c.URL, prefix, urlWithParameters), nil)
 	if err != nil {
-		failure.RuntimeErr = err
+		failure.SetRuntimeError(err)
 		return res, 0, failure
 	}
 
@@ -52,18 +52,18 @@ func (c *Client) GetRequest(urlWithParameters string, versioned ...bool) ([]byte
 
 	resp, err := c.httpClient.Do(req)
 	if err != nil {
-		failure.RuntimeErr = err
+		failure.SetRuntimeError(err)
 		return res, 0, failure
 	}
 
 	if resp.StatusCode >= http.StatusInternalServerError {
-		failure.ApiErr = fmt.Sprintf("HTTP request error. Status code: %d.\n", resp.StatusCode)
+		failure.SetApiError(fmt.Sprintf("HTTP request error. Status code: %d.\n", resp.StatusCode))
 		return res, resp.StatusCode, failure
 	}
 
 	res, err = buildRawResponse(resp)
 	if err != nil {
-		failure.RuntimeErr = err
+		failure.SetRuntimeError(err)
 	}
 
 	if c.Debug {
@@ -74,14 +74,14 @@ func (c *Client) GetRequest(urlWithParameters string, versioned ...bool) ([]byte
 }
 
 // PostRequest implements POST Request
-func (c *Client) PostRequest(url string, postParams url.Values) ([]byte, int, errs.Failure) {
+func (c *Client) PostRequest(url string, postParams url.Values) ([]byte, int, *errs.Failure) {
 	var res []byte
-	var failure errs.Failure
 	var prefix = "/api/v5"
+	failure := &errs.Failure{}
 
 	req, err := http.NewRequest("POST", fmt.Sprintf("%s%s%s", c.URL, prefix, url), strings.NewReader(postParams.Encode()))
 	if err != nil {
-		failure.RuntimeErr = err
+		failure.SetRuntimeError(err)
 		return res, 0, failure
 	}
 
@@ -94,18 +94,18 @@ func (c *Client) PostRequest(url string, postParams url.Values) ([]byte, int, er
 
 	resp, err := c.httpClient.Do(req)
 	if err != nil {
-		failure.RuntimeErr = err
+		failure.SetRuntimeError(err)
 		return res, 0, failure
 	}
 
 	if resp.StatusCode >= http.StatusInternalServerError {
-		failure.ApiErr = fmt.Sprintf("HTTP request error. Status code: %d.\n", resp.StatusCode)
+		failure.SetApiError(fmt.Sprintf("HTTP request error. Status code: %d.\n", resp.StatusCode))
 		return res, resp.StatusCode, failure
 	}
 
 	res, err = buildRawResponse(resp)
 	if err != nil {
-		failure.RuntimeErr = err
+		failure.SetRuntimeError(err)
 		return res, 0, failure
 	}
 
@@ -127,18 +127,14 @@ func buildRawResponse(resp *http.Response) ([]byte, error) {
 	return res, nil
 }
 
-func buildErr(data []byte) errs.Failure {
-	var err = errs.Failure{}
-
+func buildErr(data []byte, err *errs.Failure) {
 	resp, e := errs.ErrorResponse(data)
-	err.RuntimeErr = e
-	err.ApiErr = resp.ErrorMsg
+	err.SetRuntimeError(e)
+	err.SetApiError(resp.ErrorMsg)
 
 	if resp.Errors != nil {
-		err.ApiErrs = resp.Errors
+		err.SetApiErrors(errs.ErrorsHandler(resp.Errors))
 	}
-
-	return err
 }
 
 // checkBy select identifier type
@@ -173,7 +169,7 @@ func fillSite(p *url.Values, site []string) {
 //
 // 	data, status, err := client.APIVersions()
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -184,21 +180,22 @@ func fillSite(p *url.Values, site []string) {
 // 	for _, value := range data.versions {
 // 		fmt.Printf("%v\n", value)
 // 	}
-func (c *Client) APIVersions() (VersionResponse, int, errs.Failure) {
+func (c *Client) APIVersions() (VersionResponse, int, *errs.Failure) {
 	var resp VersionResponse
 
 	data, status, err := c.GetRequest("/api-versions", false)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // APICredentials get all available API methods for exact account
@@ -211,7 +208,7 @@ func (c *Client) APIVersions() (VersionResponse, int, errs.Failure) {
 //
 // 	data, status, err := client.APICredentials()
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -222,21 +219,22 @@ func (c *Client) APIVersions() (VersionResponse, int, errs.Failure) {
 // 	for _, value := range data.credentials {
 // 		fmt.Printf("%v\n", value)
 // 	}
-func (c *Client) APICredentials() (CredentialResponse, int, errs.Failure) {
+func (c *Client) APICredentials() (CredentialResponse, int, *errs.Failure) {
 	var resp CredentialResponse
 
 	data, status, err := c.GetRequest("/credentials", false)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Customers returns list of customers matched the specified filter
@@ -254,7 +252,7 @@ func (c *Client) APICredentials() (CredentialResponse, int, errs.Failure) {
 //		Page: 3,
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -265,23 +263,24 @@ func (c *Client) APICredentials() (CredentialResponse, int, errs.Failure) {
 // 	for _, value := range data.Customers {
 // 		fmt.Printf("%v\n", value)
 // 	}
-func (c *Client) Customers(parameters CustomersRequest) (CustomersResponse, int, errs.Failure) {
+func (c *Client) Customers(parameters CustomersRequest) (CustomersResponse, int, *errs.Failure) {
 	var resp CustomersResponse
 
 	params, _ := query.Values(parameters)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/customers?%s", params.Encode()))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // CustomersCombine combine given customers
@@ -294,14 +293,14 @@ func (c *Client) Customers(parameters CustomersRequest) (CustomersResponse, int,
 //
 // 	data, status, err := client.CustomersCombine([]v5.Customer{{ID: 1}, {ID: 2}}, Customer{ID: 3})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) CustomersCombine(customers []Customer, resultCustomer Customer) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) CustomersCombine(customers []Customer, resultCustomer Customer) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	combineJSONIn, _ := json.Marshal(&customers)
@@ -313,17 +312,18 @@ func (c *Client) CustomersCombine(customers []Customer, resultCustomer Customer)
 	}
 
 	data, status, err := c.PostRequest("/customers/combine", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // CustomerCreate creates customer
@@ -346,7 +346,7 @@ func (c *Client) CustomersCombine(customers []Customer, resultCustomer Customer)
 //		},
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -357,7 +357,7 @@ func (c *Client) CustomersCombine(customers []Customer, resultCustomer Customer)
 //	if data.Success == true {
 //		fmt.Printf("%v", err.Id)
 //	}
-func (c *Client) CustomerCreate(customer Customer, site ...string) (CustomerChangeResponse, int, errs.Failure) {
+func (c *Client) CustomerCreate(customer Customer, site ...string) (CustomerChangeResponse, int, *errs.Failure) {
 	var resp CustomerChangeResponse
 
 	customerJSON, _ := json.Marshal(&customer)
@@ -369,17 +369,18 @@ func (c *Client) CustomerCreate(customer Customer, site ...string) (CustomerChan
 	fillSite(&p, site)
 
 	data, status, err := c.PostRequest("/customers/create", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // CustomersFixExternalIds customers external ID
@@ -395,14 +396,14 @@ func (c *Client) CustomerCreate(customer Customer, site ...string) (CustomerChan
 //		ExternalID: 12,
 //	}})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) CustomersFixExternalIds(customers []IdentifiersPair) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) CustomersFixExternalIds(customers []IdentifiersPair) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	customersJSON, _ := json.Marshal(&customers)
@@ -412,17 +413,18 @@ func (c *Client) CustomersFixExternalIds(customers []IdentifiersPair) (Successfu
 	}
 
 	data, status, err := c.PostRequest("/customers/fix-external-ids", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // CustomersHistory returns customer's history
@@ -439,7 +441,7 @@ func (c *Client) CustomersFixExternalIds(customers []IdentifiersPair) (Successfu
 //		},
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -450,23 +452,24 @@ func (c *Client) CustomersFixExternalIds(customers []IdentifiersPair) (Successfu
 // 	for _, value := range data.History {
 // 		fmt.Printf("%v\n", value)
 // 	}
-func (c *Client) CustomersHistory(parameters CustomersHistoryRequest) (CustomersHistoryResponse, int, errs.Failure) {
+func (c *Client) CustomersHistory(parameters CustomersHistoryRequest) (CustomersHistoryResponse, int, *errs.Failure) {
 	var resp CustomersHistoryResponse
 
 	params, _ := query.Values(parameters)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/customers/history?%s", params.Encode()))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // CustomerNotes returns customer related notes
@@ -484,7 +487,7 @@ func (c *Client) CustomersHistory(parameters CustomersHistoryRequest) (Customers
 //		Page: 1,
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -495,23 +498,24 @@ func (c *Client) CustomersHistory(parameters CustomersHistoryRequest) (Customers
 // 	for _, value := range data.Notes {
 // 		fmt.Printf("%v\n", value)
 // 	}
-func (c *Client) CustomerNotes(parameters NotesRequest) (NotesResponse, int, errs.Failure) {
+func (c *Client) CustomerNotes(parameters NotesRequest) (NotesResponse, int, *errs.Failure) {
 	var resp NotesResponse
 
 	params, _ := query.Values(parameters)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/customers/notes?%s", params.Encode()))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // CustomerNoteCreate note creation
@@ -530,7 +534,7 @@ func (c *Client) CustomerNotes(parameters NotesRequest) (NotesResponse, int, err
 //		},
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -541,7 +545,7 @@ func (c *Client) CustomerNotes(parameters NotesRequest) (NotesResponse, int, err
 // 	if data.Success == true {
 // 		fmt.Printf("%v\n", data.ID)
 // 	}
-func (c *Client) CustomerNoteCreate(note Note, site ...string) (CreateResponse, int, errs.Failure) {
+func (c *Client) CustomerNoteCreate(note Note, site ...string) (CreateResponse, int, *errs.Failure) {
 	var resp CreateResponse
 
 	noteJSON, _ := json.Marshal(&note)
@@ -553,17 +557,18 @@ func (c *Client) CustomerNoteCreate(note Note, site ...string) (CreateResponse,
 	fillSite(&p, site)
 
 	data, status, err := c.PostRequest("/customers/notes/create", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // CustomerNoteDelete remove customer related note
@@ -575,14 +580,14 @@ func (c *Client) CustomerNoteCreate(note Note, site ...string) (CreateResponse,
 // 	var client = v5.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := client.CustomerNoteDelete(12)
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) CustomerNoteDelete(id int) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) CustomerNoteDelete(id int) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	p := url.Values{
@@ -590,17 +595,18 @@ func (c *Client) CustomerNoteDelete(id int) (SuccessfulResponse, int, errs.Failu
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/customers/notes/%d/delete", id), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // CustomersUpload customers batch upload
@@ -628,7 +634,7 @@ func (c *Client) CustomerNoteDelete(id int) (SuccessfulResponse, int, errs.Failu
 //		},
 //	}}
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -639,7 +645,7 @@ func (c *Client) CustomerNoteDelete(id int) (SuccessfulResponse, int, errs.Failu
 // 	if data.Success == true {
 // 		fmt.Printf("%v\n", data.UploadedCustomers)
 // 	}
-func (c *Client) CustomersUpload(customers []Customer, site ...string) (CustomersUploadResponse, int, errs.Failure) {
+func (c *Client) CustomersUpload(customers []Customer, site ...string) (CustomersUploadResponse, int, *errs.Failure) {
 	var resp CustomersUploadResponse
 
 	uploadJSON, _ := json.Marshal(&customers)
@@ -651,17 +657,18 @@ func (c *Client) CustomersUpload(customers []Customer, site ...string) (Customer
 	fillSite(&p, site)
 
 	data, status, err := c.PostRequest("/customers/upload", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Customer returns information about customer
@@ -674,7 +681,7 @@ func (c *Client) CustomersUpload(customers []Customer, site ...string) (Customer
 //
 // 	data, status, err := client.Customer(12, "externalId", "")
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -685,7 +692,7 @@ func (c *Client) CustomersUpload(customers []Customer, site ...string) (Customer
 // 	if data.Success == true {
 // 		fmt.Printf("%v\n", data.Customer)
 // 	}
-func (c *Client) Customer(id, by, site string) (CustomerResponse, int, errs.Failure) {
+func (c *Client) Customer(id, by, site string) (CustomerResponse, int, *errs.Failure) {
 	var resp CustomerResponse
 	var context = checkBy(by)
 
@@ -693,17 +700,18 @@ func (c *Client) Customer(id, by, site string) (CustomerResponse, int, errs.Fail
 	params, _ := query.Values(fw)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/customers/%s?%s", id, params.Encode()))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // CustomerEdit edit exact customer
@@ -725,7 +733,7 @@ func (c *Client) Customer(id, by, site string) (CustomerResponse, int, errs.Fail
 //		"id",
 //	)
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -736,7 +744,7 @@ func (c *Client) Customer(id, by, site string) (CustomerResponse, int, errs.Fail
 // 	if data.Success == true {
 // 		fmt.Printf("%v\n", data.Customer)
 // 	}
-func (c *Client) CustomerEdit(customer Customer, by string, site ...string) (CustomerChangeResponse, int, errs.Failure) {
+func (c *Client) CustomerEdit(customer Customer, by string, site ...string) (CustomerChangeResponse, int, *errs.Failure) {
 	var resp CustomerChangeResponse
 	var uid = strconv.Itoa(customer.ID)
 	var context = checkBy(by)
@@ -755,17 +763,18 @@ func (c *Client) CustomerEdit(customer Customer, by string, site ...string) (Cus
 	fillSite(&p, site)
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/customers/%s/edit", uid), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // DeliveryTracking updates tracking data
@@ -790,7 +799,7 @@ func (c *Client) CustomerEdit(customer Customer, by string, site ...string) (Cus
 //		"delivery-1",
 //	)
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -798,7 +807,7 @@ func (c *Client) CustomerEdit(customer Customer, by string, site ...string) (Cus
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
 //
-func (c *Client) DeliveryTracking(parameters DeliveryTrackingRequest, subcode string) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) DeliveryTracking(parameters DeliveryTrackingRequest, subcode string) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	updateJSON, _ := json.Marshal(&parameters)
@@ -808,17 +817,18 @@ func (c *Client) DeliveryTracking(parameters DeliveryTrackingRequest, subcode st
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/delivery/generic/%s/tracking", subcode), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // DeliveryShipments returns list of shipments
@@ -836,7 +846,7 @@ func (c *Client) DeliveryTracking(parameters DeliveryTrackingRequest, subcode st
 //		},
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -847,23 +857,24 @@ func (c *Client) DeliveryTracking(parameters DeliveryTrackingRequest, subcode st
 // 	for _, value := range data.DeliveryShipments {
 // 		fmt.Printf("%v\n", value)
 // 	}
-func (c *Client) DeliveryShipments(parameters DeliveryShipmentsRequest) (DeliveryShipmentsResponse, int, errs.Failure) {
+func (c *Client) DeliveryShipments(parameters DeliveryShipmentsRequest) (DeliveryShipmentsResponse, int, *errs.Failure) {
 	var resp DeliveryShipmentsResponse
 
 	params, _ := query.Values(parameters)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/delivery/shipments?%s", params.Encode()))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // DeliveryShipmentCreate creates shipment
@@ -886,7 +897,7 @@ func (c *Client) DeliveryShipments(parameters DeliveryShipmentsRequest) (Deliver
 //		"sdek",
 //	)
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -897,7 +908,7 @@ func (c *Client) DeliveryShipments(parameters DeliveryShipmentsRequest) (Deliver
 // 	if data.Success == true {
 // 		fmt.Printf("%v\n", data.ID)
 // 	}
-func (c *Client) DeliveryShipmentCreate(shipment DeliveryShipment, deliveryType string, site ...string) (DeliveryShipmentUpdateResponse, int, errs.Failure) {
+func (c *Client) DeliveryShipmentCreate(shipment DeliveryShipment, deliveryType string, site ...string) (DeliveryShipmentUpdateResponse, int, *errs.Failure) {
 	var resp DeliveryShipmentUpdateResponse
 	updateJSON, _ := json.Marshal(&shipment)
 
@@ -909,17 +920,18 @@ func (c *Client) DeliveryShipmentCreate(shipment DeliveryShipment, deliveryType
 	fillSite(&p, site)
 
 	data, status, err := c.PostRequest("/delivery/shipments/create", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // DeliveryShipment get information about shipment
@@ -932,7 +944,7 @@ func (c *Client) DeliveryShipmentCreate(shipment DeliveryShipment, deliveryType
 //
 // 	data, status, err := client.DeliveryShipment(12)
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -943,21 +955,22 @@ func (c *Client) DeliveryShipmentCreate(shipment DeliveryShipment, deliveryType
 // 	if data.Success == true {
 // 		fmt.Printf("%v\n", data.DeliveryShipment)
 // 	}
-func (c *Client) DeliveryShipment(id int) (DeliveryShipmentResponse, int, errs.Failure) {
+func (c *Client) DeliveryShipment(id int) (DeliveryShipmentResponse, int, *errs.Failure) {
 	var resp DeliveryShipmentResponse
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/delivery/shipments/%d", id))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // DeliveryShipmentEdit shipment editing
@@ -976,14 +989,14 @@ func (c *Client) DeliveryShipment(id int) (DeliveryShipmentResponse, int, errs.F
 //		},
 // 	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) DeliveryShipmentEdit(shipment DeliveryShipment, site ...string) (DeliveryShipmentUpdateResponse, int, errs.Failure) {
+func (c *Client) DeliveryShipmentEdit(shipment DeliveryShipment, site ...string) (DeliveryShipmentUpdateResponse, int, *errs.Failure) {
 	var resp DeliveryShipmentUpdateResponse
 	updateJSON, _ := json.Marshal(&shipment)
 
@@ -994,17 +1007,18 @@ func (c *Client) DeliveryShipmentEdit(shipment DeliveryShipment, site ...string)
 	fillSite(&p, site)
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/delivery/shipments/%s/edit", strconv.Itoa(shipment.ID)), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // IntegrationModule returns integration module
@@ -1017,7 +1031,7 @@ func (c *Client) DeliveryShipmentEdit(shipment DeliveryShipment, site ...string)
 //
 // 	data, status, err := client.IntegrationModule("moysklad3")
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -1028,21 +1042,22 @@ func (c *Client) DeliveryShipmentEdit(shipment DeliveryShipment, site ...string)
 // 	if data.Success == true {
 // 		fmt.Printf("%v\n", data.IntegrationModule)
 // 	}
-func (c *Client) IntegrationModule(code string) (IntegrationModuleResponse, int, errs.Failure) {
+func (c *Client) IntegrationModule(code string) (IntegrationModuleResponse, int, *errs.Failure) {
 	var resp IntegrationModuleResponse
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/integration-modules/%s", code))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // IntegrationModuleEdit integration module create/edit
@@ -1067,7 +1082,7 @@ func (c *Client) IntegrationModule(code string) (IntegrationModuleResponse, int,
 //		Logo:            "https://cdn.worldvectorlogo.com/logos/github-icon.svg",
 //	})
 //
-//	if err.RuntimeErr != nil {
+//	if err.Error() != "" {
 //		fmt.Printf("%v", err.RuntimeErr)
 //	}
 //
@@ -1078,24 +1093,25 @@ func (c *Client) IntegrationModule(code string) (IntegrationModuleResponse, int,
 //	if data.Success == true {
 //		fmt.Printf("%v\n", data.Info)
 //	}
-func (c *Client) IntegrationModuleEdit(integrationModule IntegrationModule) (IntegrationModuleEditResponse, int, errs.Failure) {
+func (c *Client) IntegrationModuleEdit(integrationModule IntegrationModule) (IntegrationModuleEditResponse, int, *errs.Failure) {
 	var resp IntegrationModuleEditResponse
 	updateJSON, _ := json.Marshal(&integrationModule)
 
 	p := url.Values{"integrationModule": {string(updateJSON[:])}}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/integration-modules/%s/edit", integrationModule.Code), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Orders returns list of orders matched the specified filters
@@ -1108,7 +1124,7 @@ func (c *Client) IntegrationModuleEdit(integrationModule IntegrationModule) (Int
 //
 // 	data, status, err := client.Orders(v5.OrdersRequest{Filter: v5.OrdersFilter{City: "Moscow"}, Page: 1})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -1119,23 +1135,24 @@ func (c *Client) IntegrationModuleEdit(integrationModule IntegrationModule) (Int
 // 	for _, value := range data.Orders {
 // 		fmt.Printf("%v\n", value)
 // 	}
-func (c *Client) Orders(parameters OrdersRequest) (OrdersResponse, int, errs.Failure) {
+func (c *Client) Orders(parameters OrdersRequest) (OrdersResponse, int, *errs.Failure) {
 	var resp OrdersResponse
 
 	params, _ := query.Values(parameters)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/orders?%s", params.Encode()))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // OrdersCombine combines given orders
@@ -1148,14 +1165,14 @@ func (c *Client) Orders(parameters OrdersRequest) (OrdersResponse, int, errs.Fai
 //
 // 	data, status, err := client.OrdersCombine("ours", v5.Order{ID: 1}, v5.Order{ID: 1})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) OrdersCombine(technique string, order, resultOrder Order) (OperationResponse, int, errs.Failure) {
+func (c *Client) OrdersCombine(technique string, order, resultOrder Order) (OperationResponse, int, *errs.Failure) {
 	var resp OperationResponse
 
 	combineJSONIn, _ := json.Marshal(&order)
@@ -1168,17 +1185,18 @@ func (c *Client) OrdersCombine(technique string, order, resultOrder Order) (Oper
 	}
 
 	data, status, err := c.PostRequest("/orders/combine", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // OrderCreate creates an order
@@ -1197,7 +1215,7 @@ func (c *Client) OrdersCombine(technique string, order, resultOrder Order) (Oper
 //		Items:      []v5.OrderItem{{Offer: v5.Offer{ID: 12}, Quantity: 5}},
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -1208,7 +1226,7 @@ func (c *Client) OrdersCombine(technique string, order, resultOrder Order) (Oper
 // 	if data.Success == true {
 // 		fmt.Printf("%v\n", data.ID)
 // 	}
-func (c *Client) OrderCreate(order Order, site ...string) (CreateResponse, int, errs.Failure) {
+func (c *Client) OrderCreate(order Order, site ...string) (CreateResponse, int, *errs.Failure) {
 	var resp CreateResponse
 	orderJSON, _ := json.Marshal(&order)
 
@@ -1219,17 +1237,18 @@ func (c *Client) OrderCreate(order Order, site ...string) (CreateResponse, int,
 	fillSite(&p, site)
 
 	data, status, err := c.PostRequest("/orders/create", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // OrdersFixExternalIds set order external ID
@@ -1245,7 +1264,7 @@ func (c *Client) OrderCreate(order Order, site ...string) (CreateResponse, int,
 //		ExternalID: 12,
 //	}})
 //
-//	if err.RuntimeErr != nil {
+//	if err.Error() != "" {
 //		fmt.Printf("%v", err.RuntimeErr)
 //	}
 //
@@ -1256,7 +1275,7 @@ func (c *Client) OrderCreate(order Order, site ...string) (CreateResponse, int,
 //	if data.Success == true {
 //		fmt.Printf("%v\n", data.ID)
 //	}
-func (c *Client) OrdersFixExternalIds(orders []IdentifiersPair) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) OrdersFixExternalIds(orders []IdentifiersPair) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	ordersJSON, _ := json.Marshal(&orders)
@@ -1266,17 +1285,18 @@ func (c *Client) OrdersFixExternalIds(orders []IdentifiersPair) (SuccessfulRespo
 	}
 
 	data, status, err := c.PostRequest("/orders/fix-external-ids", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // OrdersHistory returns orders history
@@ -1289,7 +1309,7 @@ func (c *Client) OrdersFixExternalIds(orders []IdentifiersPair) (SuccessfulRespo
 //
 // 	data, status, err := client.OrdersHistory(v5.OrdersHistoryRequest{Filter: v5.OrdersHistoryFilter{SinceID: 20}})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -1300,23 +1320,24 @@ func (c *Client) OrdersFixExternalIds(orders []IdentifiersPair) (SuccessfulRespo
 // 	for _, value := range data.History {
 // 		fmt.Printf("%v\n", value)
 // 	}
-func (c *Client) OrdersHistory(parameters OrdersHistoryRequest) (CustomersHistoryResponse, int, errs.Failure) {
+func (c *Client) OrdersHistory(parameters OrdersHistoryRequest) (CustomersHistoryResponse, int, *errs.Failure) {
 	var resp CustomersHistoryResponse
 
 	params, _ := query.Values(parameters)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/orders/history?%s", params.Encode()))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // OrderPaymentCreate creates payment
@@ -1335,7 +1356,7 @@ func (c *Client) OrdersHistory(parameters OrdersHistoryRequest) (CustomersHistor
 //		Type:   "cash",
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -1346,7 +1367,7 @@ func (c *Client) OrdersHistory(parameters OrdersHistoryRequest) (CustomersHistor
 //	if data.Success == true {
 // 		fmt.Printf("%v\n", data.ID)
 // 	}
-func (c *Client) OrderPaymentCreate(payment Payment, site ...string) (CreateResponse, int, errs.Failure) {
+func (c *Client) OrderPaymentCreate(payment Payment, site ...string) (CreateResponse, int, *errs.Failure) {
 	var resp CreateResponse
 
 	paymentJSON, _ := json.Marshal(&payment)
@@ -1358,17 +1379,18 @@ func (c *Client) OrderPaymentCreate(payment Payment, site ...string) (CreateResp
 	fillSite(&p, site)
 
 	data, status, err := c.PostRequest("/orders/payments/create", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // OrderPaymentDelete payment removing
@@ -1381,14 +1403,14 @@ func (c *Client) OrderPaymentCreate(payment Payment, site ...string) (CreateResp
 //
 // 	data, status, err := client.OrderPaymentDelete(12)
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) OrderPaymentDelete(id int) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) OrderPaymentDelete(id int) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	p := url.Values{
@@ -1396,17 +1418,18 @@ func (c *Client) OrderPaymentDelete(id int) (SuccessfulResponse, int, errs.Failu
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/orders/payments/%d/delete", id), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // OrderPaymentEdit edit payment
@@ -1425,14 +1448,14 @@ func (c *Client) OrderPaymentDelete(id int) (SuccessfulResponse, int, errs.Failu
 //		"id",
 //	)
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) OrderPaymentEdit(payment Payment, by string, site ...string) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) OrderPaymentEdit(payment Payment, by string, site ...string) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 	var uid = strconv.Itoa(payment.ID)
 	var context = checkBy(by)
@@ -1450,17 +1473,18 @@ func (c *Client) OrderPaymentEdit(payment Payment, by string, site ...string) (S
 	fillSite(&p, site)
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/orders/payments/%s/edit", uid), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // OrdersUpload batch orders uploading
@@ -1488,7 +1512,7 @@ func (c *Client) OrderPaymentEdit(payment Payment, by string, site ...string) (S
 //		}
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -1499,7 +1523,7 @@ func (c *Client) OrderPaymentEdit(payment Payment, by string, site ...string) (S
 //	if data.Success == true {
 // 		fmt.Printf("%v\n", data.UploadedOrders)
 // 	}
-func (c *Client) OrdersUpload(orders []Order, site ...string) (OrdersUploadResponse, int, errs.Failure) {
+func (c *Client) OrdersUpload(orders []Order, site ...string) (OrdersUploadResponse, int, *errs.Failure) {
 	var resp OrdersUploadResponse
 
 	uploadJSON, _ := json.Marshal(&orders)
@@ -1511,17 +1535,18 @@ func (c *Client) OrdersUpload(orders []Order, site ...string) (OrdersUploadRespo
 	fillSite(&p, site)
 
 	data, status, err := c.PostRequest("/orders/upload", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Order returns information about order
@@ -1534,7 +1559,7 @@ func (c *Client) OrdersUpload(orders []Order, site ...string) (OrdersUploadRespo
 //
 // 	data, status, err := client.Order(12, "externalId", "")
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -1545,7 +1570,7 @@ func (c *Client) OrdersUpload(orders []Order, site ...string) (OrdersUploadRespo
 //	if data.Success == true {
 // 		fmt.Printf("%v\n", data.Order)
 // 	}
-func (c *Client) Order(id, by, site string) (OrderResponse, int, errs.Failure) {
+func (c *Client) Order(id, by, site string) (OrderResponse, int, *errs.Failure) {
 	var resp OrderResponse
 	var context = checkBy(by)
 
@@ -1553,17 +1578,18 @@ func (c *Client) Order(id, by, site string) (OrderResponse, int, errs.Failure) {
 	params, _ := query.Values(fw)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/orders/%s?%s", id, params.Encode()))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // OrderEdit edit an order
@@ -1582,14 +1608,14 @@ func (c *Client) Order(id, by, site string) (OrderResponse, int, errs.Failure) {
 // 		"id",
 // 	)
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) OrderEdit(order Order, by string, site ...string) (CreateResponse, int, errs.Failure) {
+func (c *Client) OrderEdit(order Order, by string, site ...string) (CreateResponse, int, *errs.Failure) {
 	var resp CreateResponse
 	var uid = strconv.Itoa(order.ID)
 	var context = checkBy(by)
@@ -1608,17 +1634,18 @@ func (c *Client) OrderEdit(order Order, by string, site ...string) (CreateRespon
 	fillSite(&p, site)
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/orders/%s/edit", uid), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Packs returns list of packs matched the specified filters
@@ -1631,7 +1658,7 @@ func (c *Client) OrderEdit(order Order, by string, site ...string) (CreateRespon
 //
 // 	data, status, err := client.Packs(v5.PacksRequest{Filter: v5.PacksFilter{OrderID: 12}})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -1642,23 +1669,24 @@ func (c *Client) OrderEdit(order Order, by string, site ...string) (CreateRespon
 //	for _, value := range data.Packs {
 // 		fmt.Printf("%v\n", value)
 // 	}
-func (c *Client) Packs(parameters PacksRequest) (PacksResponse, int, errs.Failure) {
+func (c *Client) Packs(parameters PacksRequest) (PacksResponse, int, *errs.Failure) {
 	var resp PacksResponse
 
 	params, _ := query.Values(parameters)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/orders/packs?%s", params.Encode()))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // PackCreate creates a pack
@@ -1675,7 +1703,7 @@ func (c *Client) Packs(parameters PacksRequest) (PacksResponse, int, errs.Failur
 //		Quantity: 1,
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -1686,7 +1714,7 @@ func (c *Client) Packs(parameters PacksRequest) (PacksResponse, int, errs.Failur
 //	if data.Success == true {
 // 		fmt.Printf("%v\n", data.ID)
 // 	}
-func (c *Client) PackCreate(pack Pack) (CreateResponse, int, errs.Failure) {
+func (c *Client) PackCreate(pack Pack) (CreateResponse, int, *errs.Failure) {
 	var resp CreateResponse
 	packJSON, _ := json.Marshal(&pack)
 
@@ -1695,17 +1723,18 @@ func (c *Client) PackCreate(pack Pack) (CreateResponse, int, errs.Failure) {
 	}
 
 	data, status, err := c.PostRequest("/orders/packs/create", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // PacksHistory returns a history of order packing
@@ -1718,7 +1747,7 @@ func (c *Client) PackCreate(pack Pack) (CreateResponse, int, errs.Failure) {
 //
 // 	data, status, err := client.PacksHistory(v5.PacksHistoryRequest{Filter: v5.OrdersHistoryFilter{SinceID: 5}})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -1729,23 +1758,24 @@ func (c *Client) PackCreate(pack Pack) (CreateResponse, int, errs.Failure) {
 //	for _, value := range data.History {
 // 		fmt.Printf("%v\n", value)
 // 	}
-func (c *Client) PacksHistory(parameters PacksHistoryRequest) (PacksHistoryResponse, int, errs.Failure) {
+func (c *Client) PacksHistory(parameters PacksHistoryRequest) (PacksHistoryResponse, int, *errs.Failure) {
 	var resp PacksHistoryResponse
 
 	params, _ := query.Values(parameters)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/orders/packs/history?%s", params.Encode()))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Pack returns a pack info
@@ -1758,7 +1788,7 @@ func (c *Client) PacksHistory(parameters PacksHistoryRequest) (PacksHistoryRespo
 //
 // 	data, status, err := client.Pack(112)
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -1769,21 +1799,22 @@ func (c *Client) PacksHistory(parameters PacksHistoryRequest) (PacksHistoryRespo
 //	if data.Success == true {
 // 		fmt.Printf("%v\n", data.Pack)
 // 	}
-func (c *Client) Pack(id int) (PackResponse, int, errs.Failure) {
+func (c *Client) Pack(id int) (PackResponse, int, *errs.Failure) {
 	var resp PackResponse
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/orders/packs/%d", id))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // PackDelete removes a pack
@@ -1796,28 +1827,29 @@ func (c *Client) Pack(id int) (PackResponse, int, errs.Failure) {
 //
 // 	data, status, err := client.PackDelete(112)
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) PackDelete(id int) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) PackDelete(id int) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/orders/packs/%d/delete", id), url.Values{})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // PackEdit edit a pack
@@ -1830,14 +1862,14 @@ func (c *Client) PackDelete(id int) (SuccessfulResponse, int, errs.Failure) {
 //
 // 	data, status, err := client.PackEdit(Pack{ID: 12, Quantity: 2})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) PackEdit(pack Pack) (CreateResponse, int, errs.Failure) {
+func (c *Client) PackEdit(pack Pack) (CreateResponse, int, *errs.Failure) {
 	var resp CreateResponse
 
 	packJSON, _ := json.Marshal(&pack)
@@ -1847,57 +1879,60 @@ func (c *Client) PackEdit(pack Pack) (CreateResponse, int, errs.Failure) {
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/orders/packs/%d/edit", pack.ID), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Countries returns list of available country codes
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-reference-countries
-func (c *Client) Countries() (CountriesResponse, int, errs.Failure) {
+func (c *Client) Countries() (CountriesResponse, int, *errs.Failure) {
 	var resp CountriesResponse
 
 	data, status, err := c.GetRequest("/reference/countries")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // CostGroups returns costs groups list
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-reference-cost-groups
-func (c *Client) CostGroups() (CostGroupsResponse, int, errs.Failure) {
+func (c *Client) CostGroups() (CostGroupsResponse, int, *errs.Failure) {
 	var resp CostGroupsResponse
 
 	data, status, err := c.GetRequest("/reference/cost-groups")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // CostGroupEdit edit costs groups
@@ -1913,14 +1948,14 @@ func (c *Client) CostGroups() (CostGroupsResponse, int, errs.Failure) {
 //		Color:  "#da5c98",
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) CostGroupEdit(costGroup CostGroup) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) CostGroupEdit(costGroup CostGroup) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	objJSON, _ := json.Marshal(&costGroup)
@@ -1930,37 +1965,39 @@ func (c *Client) CostGroupEdit(costGroup CostGroup) (SuccessfulResponse, int, er
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/cost-groups/%s/edit", costGroup.Code), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // CostItems returns costs items list
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-reference-cost-items
-func (c *Client) CostItems() (CostItemsResponse, int, errs.Failure) {
+func (c *Client) CostItems() (CostItemsResponse, int, *errs.Failure) {
 	var resp CostItemsResponse
 
 	data, status, err := c.GetRequest("/reference/cost-items")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // CostItemEdit edit costs items
@@ -1976,14 +2013,14 @@ func (c *Client) CostItems() (CostItemsResponse, int, errs.Failure) {
 //		Active:          false,
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) CostItemEdit(costItem CostItem) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) CostItemEdit(costItem CostItem) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	objJSON, _ := json.Marshal(&costItem)
@@ -1993,37 +2030,39 @@ func (c *Client) CostItemEdit(costItem CostItem) (SuccessfulResponse, int, errs.
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/cost-items/%s/edit", costItem.Code), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Couriers returns list of couriers
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-reference-couriers
-func (c *Client) Couriers() (CouriersResponse, int, errs.Failure) {
+func (c *Client) Couriers() (CouriersResponse, int, *errs.Failure) {
 	var resp CouriersResponse
 
 	data, status, err := c.GetRequest("/reference/couriers")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // CourierCreate creates a courier
@@ -2041,7 +2080,7 @@ func (c *Client) Couriers() (CouriersResponse, int, errs.Failure) {
 //		LastName:  "Ivanov",
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -2052,7 +2091,7 @@ func (c *Client) Couriers() (CouriersResponse, int, errs.Failure) {
 // 	if data.Success == true {
 // 		fmt.Printf("%v", data.ID)
 // 	}
-func (c *Client) CourierCreate(courier Courier) (CreateResponse, int, errs.Failure) {
+func (c *Client) CourierCreate(courier Courier) (CreateResponse, int, *errs.Failure) {
 	var resp CreateResponse
 
 	objJSON, _ := json.Marshal(&courier)
@@ -2062,17 +2101,18 @@ func (c *Client) CourierCreate(courier Courier) (CreateResponse, int, errs.Failu
 	}
 
 	data, status, err := c.PostRequest("/reference/couriers/create", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // CourierEdit edit a courier
@@ -2088,14 +2128,14 @@ func (c *Client) CourierCreate(courier Courier) (CreateResponse, int, errs.Failu
 //		Patronymic: "Ivanovich",
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) CourierEdit(courier Courier) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) CourierEdit(courier Courier) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	objJSON, _ := json.Marshal(&courier)
@@ -2105,37 +2145,39 @@ func (c *Client) CourierEdit(courier Courier) (SuccessfulResponse, int, errs.Fai
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/couriers/%d/edit", courier.ID), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // DeliveryServices returns list of delivery services
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-reference-delivery-services
-func (c *Client) DeliveryServices() (DeliveryServiceResponse, int, errs.Failure) {
+func (c *Client) DeliveryServices() (DeliveryServiceResponse, int, *errs.Failure) {
 	var resp DeliveryServiceResponse
 
 	data, status, err := c.GetRequest("/reference/delivery-services")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // DeliveryServiceEdit delivery service create/edit
@@ -2151,14 +2193,14 @@ func (c *Client) DeliveryServices() (DeliveryServiceResponse, int, errs.Failure)
 //		Code:   "delivery-1",
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) DeliveryServiceEdit(deliveryService DeliveryService) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) DeliveryServiceEdit(deliveryService DeliveryService) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	objJSON, _ := json.Marshal(&deliveryService)
@@ -2168,37 +2210,39 @@ func (c *Client) DeliveryServiceEdit(deliveryService DeliveryService) (Successfu
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/delivery-services/%s/edit", deliveryService.Code), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // DeliveryTypes returns list of delivery types
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-reference-delivery-types
-func (c *Client) DeliveryTypes() (DeliveryTypesResponse, int, errs.Failure) {
+func (c *Client) DeliveryTypes() (DeliveryTypesResponse, int, *errs.Failure) {
 	var resp DeliveryTypesResponse
 
 	data, status, err := c.GetRequest("/reference/delivery-types")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // DeliveryTypeEdit delivery type create/edit
@@ -2216,14 +2260,14 @@ func (c *Client) DeliveryTypes() (DeliveryTypesResponse, int, errs.Failure) {
 //		DefaultForCrm: false,
 //	}
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) DeliveryTypeEdit(deliveryType DeliveryType) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) DeliveryTypeEdit(deliveryType DeliveryType) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	objJSON, _ := json.Marshal(&deliveryType)
@@ -2233,37 +2277,39 @@ func (c *Client) DeliveryTypeEdit(deliveryType DeliveryType) (SuccessfulResponse
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/delivery-types/%s/edit", deliveryType.Code), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // LegalEntities returns list of legal entities
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-reference-legal-entities
-func (c *Client) LegalEntities() (LegalEntitiesResponse, int, errs.Failure) {
+func (c *Client) LegalEntities() (LegalEntitiesResponse, int, *errs.Failure) {
 	var resp LegalEntitiesResponse
 
 	data, status, err := c.GetRequest("/reference/legal-entities")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // LegalEntityEdit change information about legal entity
@@ -2279,14 +2325,14 @@ func (c *Client) LegalEntities() (LegalEntitiesResponse, int, errs.Failure) {
 //		CertificateDate:   "2012-12-12",
 //	}
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) LegalEntityEdit(legalEntity LegalEntity) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) LegalEntityEdit(legalEntity LegalEntity) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	objJSON, _ := json.Marshal(&legalEntity)
@@ -2296,37 +2342,39 @@ func (c *Client) LegalEntityEdit(legalEntity LegalEntity) (SuccessfulResponse, i
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/legal-entities/%s/edit", legalEntity.Code), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // OrderMethods returns list of order methods
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-reference-order-methods
-func (c *Client) OrderMethods() (OrderMethodsResponse, int, errs.Failure) {
+func (c *Client) OrderMethods() (OrderMethodsResponse, int, *errs.Failure) {
 	var resp OrderMethodsResponse
 
 	data, status, err := c.GetRequest("/reference/order-methods")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // OrderMethodEdit order method create/edit
@@ -2343,14 +2391,14 @@ func (c *Client) OrderMethods() (OrderMethodsResponse, int, errs.Failure) {
 //		DefaultForCRM: false,
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) OrderMethodEdit(orderMethod OrderMethod) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) OrderMethodEdit(orderMethod OrderMethod) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	objJSON, _ := json.Marshal(&orderMethod)
@@ -2360,37 +2408,39 @@ func (c *Client) OrderMethodEdit(orderMethod OrderMethod) (SuccessfulResponse, i
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/order-methods/%s/edit", orderMethod.Code), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // OrderTypes return list of order types
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-reference-order-types
-func (c *Client) OrderTypes() (OrderTypesResponse, int, errs.Failure) {
+func (c *Client) OrderTypes() (OrderTypesResponse, int, *errs.Failure) {
 	var resp OrderTypesResponse
 
 	data, status, err := c.GetRequest("/reference/order-types")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // OrderTypeEdit create/edit order type
@@ -2407,14 +2457,14 @@ func (c *Client) OrderTypes() (OrderTypesResponse, int, errs.Failure) {
 //		DefaultForCRM: false,
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) OrderTypeEdit(orderType OrderType) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) OrderTypeEdit(orderType OrderType) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	objJSON, _ := json.Marshal(&orderType)
@@ -2424,43 +2474,45 @@ func (c *Client) OrderTypeEdit(orderType OrderType) (SuccessfulResponse, int, er
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/order-types/%s/edit", orderType.Code), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // PaymentStatuses returns list of payment statuses
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-reference-payment-statuses
-func (c *Client) PaymentStatuses() (PaymentStatusesResponse, int, errs.Failure) {
+func (c *Client) PaymentStatuses() (PaymentStatusesResponse, int, *errs.Failure) {
 	var resp PaymentStatusesResponse
 
 	data, status, err := c.GetRequest("/reference/payment-statuses")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // PaymentStatusEdit payment status creation/editing
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#post--api-v5-reference-payment-statuses-code-edit
-func (c *Client) PaymentStatusEdit(paymentStatus PaymentStatus) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) PaymentStatusEdit(paymentStatus PaymentStatus) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	objJSON, _ := json.Marshal(&paymentStatus)
@@ -2470,43 +2522,45 @@ func (c *Client) PaymentStatusEdit(paymentStatus PaymentStatus) (SuccessfulRespo
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/payment-statuses/%s/edit", paymentStatus.Code), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // PaymentTypes returns list of payment types
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-reference-payment-types
-func (c *Client) PaymentTypes() (PaymentTypesResponse, int, errs.Failure) {
+func (c *Client) PaymentTypes() (PaymentTypesResponse, int, *errs.Failure) {
 	var resp PaymentTypesResponse
 
 	data, status, err := c.GetRequest("/reference/payment-types")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // PaymentTypeEdit payment type create/edit
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#post--api-v5-reference-payment-types-code-edit
-func (c *Client) PaymentTypeEdit(paymentType PaymentType) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) PaymentTypeEdit(paymentType PaymentType) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	objJSON, _ := json.Marshal(&paymentType)
@@ -2516,43 +2570,45 @@ func (c *Client) PaymentTypeEdit(paymentType PaymentType) (SuccessfulResponse, i
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/payment-types/%s/edit", paymentType.Code), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // PriceTypes returns list of price types
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-reference-price-types
-func (c *Client) PriceTypes() (PriceTypesResponse, int, errs.Failure) {
+func (c *Client) PriceTypes() (PriceTypesResponse, int, *errs.Failure) {
 	var resp PriceTypesResponse
 
 	data, status, err := c.GetRequest("/reference/price-types")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // PriceTypeEdit price type create/edit
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#post--api-v5-reference-price-types-code-edit
-func (c *Client) PriceTypeEdit(priceType PriceType) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) PriceTypeEdit(priceType PriceType) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	objJSON, _ := json.Marshal(&priceType)
@@ -2562,43 +2618,45 @@ func (c *Client) PriceTypeEdit(priceType PriceType) (SuccessfulResponse, int, er
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/price-types/%s/edit", priceType.Code), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // ProductStatuses returns list of item statuses in order
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-reference-product-statuses
-func (c *Client) ProductStatuses() (ProductStatusesResponse, int, errs.Failure) {
+func (c *Client) ProductStatuses() (ProductStatusesResponse, int, *errs.Failure) {
 	var resp ProductStatusesResponse
 
 	data, status, err := c.GetRequest("/reference/product-statuses")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // ProductStatusEdit order item status create/edit
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#post--api-v5-reference-product-statuses-code-edit
-func (c *Client) ProductStatusEdit(productStatus ProductStatus) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) ProductStatusEdit(productStatus ProductStatus) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	objJSON, _ := json.Marshal(&productStatus)
@@ -2608,43 +2666,45 @@ func (c *Client) ProductStatusEdit(productStatus ProductStatus) (SuccessfulRespo
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/product-statuses/%s/edit", productStatus.Code), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Sites returns the sites list
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-reference-sites
-func (c *Client) Sites() (SitesResponse, int, errs.Failure) {
+func (c *Client) Sites() (SitesResponse, int, *errs.Failure) {
 	var resp SitesResponse
 
 	data, status, err := c.GetRequest("/reference/sites")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // SiteEdit site create/edit
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#post--api-v5-reference-sites-code-edit
-func (c *Client) SiteEdit(site Site) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) SiteEdit(site Site) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	objJSON, _ := json.Marshal(&site)
@@ -2654,63 +2714,66 @@ func (c *Client) SiteEdit(site Site) (SuccessfulResponse, int, errs.Failure) {
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/sites/%s/edit", site.Code), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // StatusGroups returns list of order status groups
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-reference-status-groups
-func (c *Client) StatusGroups() (StatusGroupsResponse, int, errs.Failure) {
+func (c *Client) StatusGroups() (StatusGroupsResponse, int, *errs.Failure) {
 	var resp StatusGroupsResponse
 
 	data, status, err := c.GetRequest("/reference/status-groups")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Statuses returns list of order statuses
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-reference-statuses
-func (c *Client) Statuses() (StatusesResponse, int, errs.Failure) {
+func (c *Client) Statuses() (StatusesResponse, int, *errs.Failure) {
 	var resp StatusesResponse
 
 	data, status, err := c.GetRequest("/reference/statuses")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // StatusEdit order status create/edit
 //
 // For more information see www.retailcrm.pro/docs/Developers/ApiVersion5#post--api-v5-reference-sites-code-edit
-func (c *Client) StatusEdit(st Status) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) StatusEdit(st Status) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	objJSON, _ := json.Marshal(&st)
@@ -2720,43 +2783,45 @@ func (c *Client) StatusEdit(st Status) (SuccessfulResponse, int, errs.Failure) {
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/statuses/%s/edit", st.Code), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Stores returns list of warehouses
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-reference-stores
-func (c *Client) Stores() (StoresResponse, int, errs.Failure) {
+func (c *Client) Stores() (StoresResponse, int, *errs.Failure) {
 	var resp StoresResponse
 
 	data, status, err := c.GetRequest("/reference/stores")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // StoreEdit warehouse create/edit
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#post--api-v5-reference-stores-code-edit
-func (c *Client) StoreEdit(store Store) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) StoreEdit(store Store) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	objJSON, _ := json.Marshal(&store)
@@ -2766,43 +2831,45 @@ func (c *Client) StoreEdit(store Store) (SuccessfulResponse, int, errs.Failure)
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/stores/%s/edit", store.Code), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Units returns units list
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-reference-units
-func (c *Client) Units() (UnitsResponse, int, errs.Failure) {
+func (c *Client) Units() (UnitsResponse, int, *errs.Failure) {
 	var resp UnitsResponse
 
 	data, status, err := c.GetRequest("/reference/units")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // UnitEdit unit create/edit
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#post--api-v5-reference-units-code-edit
-func (c *Client) UnitEdit(unit Unit) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) UnitEdit(unit Unit) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	objJSON, _ := json.Marshal(&unit)
@@ -2812,17 +2879,18 @@ func (c *Client) UnitEdit(unit Unit) (SuccessfulResponse, int, errs.Failure) {
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/units/%s/edit", unit.Code), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Segments returns segments
@@ -2839,7 +2907,7 @@ func (c *Client) UnitEdit(unit Unit) (SuccessfulResponse, int, errs.Failure) {
 //		}
 //	})
 //
-//	if err.RuntimeErr != nil {
+//	if err.Error() != "" {
 //		fmt.Printf("%v", err.RuntimeErr)
 //	}
 //
@@ -2850,23 +2918,24 @@ func (c *Client) UnitEdit(unit Unit) (SuccessfulResponse, int, errs.Failure) {
 //	for _, value := range data.Segments {
 //		fmt.Printf("%v\n", value)
 //	}
-func (c *Client) Segments(parameters SegmentsRequest) (SegmentsResponse, int, errs.Failure) {
+func (c *Client) Segments(parameters SegmentsRequest) (SegmentsResponse, int, *errs.Failure) {
 	var resp SegmentsResponse
 
 	params, _ := query.Values(parameters)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/segments?%s", params.Encode()))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Inventories returns leftover stocks and purchasing prices
@@ -2879,7 +2948,7 @@ func (c *Client) Segments(parameters SegmentsRequest) (SegmentsResponse, int, er
 //
 // 	data, status, err := client.Inventories(v5.InventoriesRequest{Filter: v5.InventoriesFilter{Details: 1, ProductActive: 1}, Page: 1})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -2890,23 +2959,24 @@ func (c *Client) Segments(parameters SegmentsRequest) (SegmentsResponse, int, er
 //	for _, value := range data.Offers {
 // 		fmt.Printf("%v\n", value)
 // 	}
-func (c *Client) Inventories(parameters InventoriesRequest) (InventoriesResponse, int, errs.Failure) {
+func (c *Client) Inventories(parameters InventoriesRequest) (InventoriesResponse, int, *errs.Failure) {
 	var resp InventoriesResponse
 
 	params, _ := query.Values(parameters)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/store/inventories?%s", params.Encode()))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // InventoriesUpload updates the leftover stocks and purchasing prices
@@ -2938,7 +3008,7 @@ func (c *Client) Inventories(parameters InventoriesRequest) (InventoriesResponse
 //	   },
 //	)
 //
-//	if err.RuntimeErr != nil {
+//	if err.Error() != "" {
 //		fmt.Printf("%v", err.RuntimeErr)
 //	}
 //
@@ -2947,7 +3017,7 @@ func (c *Client) Inventories(parameters InventoriesRequest) (InventoriesResponse
 //	}
 //
 //	fmt.Printf("%v\n", data.NotFoundOffers)
-func (c *Client) InventoriesUpload(inventories []InventoryUpload, site ...string) (StoreUploadResponse, int, errs.Failure) {
+func (c *Client) InventoriesUpload(inventories []InventoryUpload, site ...string) (StoreUploadResponse, int, *errs.Failure) {
 	var resp StoreUploadResponse
 
 	uploadJSON, _ := json.Marshal(&inventories)
@@ -2959,17 +3029,18 @@ func (c *Client) InventoriesUpload(inventories []InventoryUpload, site ...string
 	fillSite(&p, site)
 
 	data, status, err := c.PostRequest("/store/inventories/upload", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // PricesUpload updates prices
@@ -2993,7 +3064,7 @@ func (c *Client) InventoriesUpload(inventories []InventoryUpload, site ...string
 //		},
 //	})
 //
-//	if err.RuntimeErr != nil {
+//	if err.Error() != "" {
 //		fmt.Printf("%v", err.RuntimeErr)
 //	}
 //
@@ -3002,7 +3073,7 @@ func (c *Client) InventoriesUpload(inventories []InventoryUpload, site ...string
 //	}
 //
 //	fmt.Printf("%v\n", data.NotFoundOffers)
-func (c *Client) PricesUpload(prices []OfferPriceUpload) (StoreUploadResponse, int, errs.Failure) {
+func (c *Client) PricesUpload(prices []OfferPriceUpload) (StoreUploadResponse, int, *errs.Failure) {
 	var resp StoreUploadResponse
 
 	uploadJSON, _ := json.Marshal(&prices)
@@ -3012,17 +3083,18 @@ func (c *Client) PricesUpload(prices []OfferPriceUpload) (StoreUploadResponse, i
 	}
 
 	data, status, err := c.PostRequest("/store/prices/upload", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // ProductsGroup returns list of product groups
@@ -3039,7 +3111,7 @@ func (c *Client) PricesUpload(prices []OfferPriceUpload) (StoreUploadResponse, i
 //		},
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -3050,23 +3122,24 @@ func (c *Client) PricesUpload(prices []OfferPriceUpload) (StoreUploadResponse, i
 //	for _, value := range data.ProductGroup {
 // 		fmt.Printf("%v\n", value)
 // 	}
-func (c *Client) ProductsGroup(parameters ProductsGroupsRequest) (ProductsGroupsResponse, int, errs.Failure) {
+func (c *Client) ProductsGroup(parameters ProductsGroupsRequest) (ProductsGroupsResponse, int, *errs.Failure) {
 	var resp ProductsGroupsResponse
 
 	params, _ := query.Values(parameters)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/store/product-groups?%s", params.Encode()))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Products returns list of products and SKU
@@ -3084,7 +3157,7 @@ func (c *Client) ProductsGroup(parameters ProductsGroupsRequest) (ProductsGroups
 //		},
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -3095,23 +3168,24 @@ func (c *Client) ProductsGroup(parameters ProductsGroupsRequest) (ProductsGroups
 //	for _, value := range data.Products {
 // 		fmt.Printf("%v\n", value)
 // 	}
-func (c *Client) Products(parameters ProductsRequest) (ProductsResponse, int, errs.Failure) {
+func (c *Client) Products(parameters ProductsRequest) (ProductsResponse, int, *errs.Failure) {
 	var resp ProductsResponse
 
 	params, _ := query.Values(parameters)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/store/products?%s", params.Encode()))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // ProductsProperties returns list of item properties, matching the specified filters
@@ -3128,7 +3202,7 @@ func (c *Client) Products(parameters ProductsRequest) (ProductsResponse, int, er
 //		},
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -3139,23 +3213,24 @@ func (c *Client) Products(parameters ProductsRequest) (ProductsResponse, int, er
 //	for _, value := range data.Properties {
 // 		fmt.Printf("%v\n", value)
 // 	}
-func (c *Client) ProductsProperties(parameters ProductsPropertiesRequest) (ProductsPropertiesResponse, int, errs.Failure) {
+func (c *Client) ProductsProperties(parameters ProductsPropertiesRequest) (ProductsPropertiesResponse, int, *errs.Failure) {
 	var resp ProductsPropertiesResponse
 
 	params, _ := query.Values(parameters)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/store/products/properties?%s", params.Encode()))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Tasks returns task list
@@ -3172,7 +3247,7 @@ func (c *Client) ProductsProperties(parameters ProductsPropertiesRequest) (Produ
 //		},
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -3183,23 +3258,24 @@ func (c *Client) ProductsProperties(parameters ProductsPropertiesRequest) (Produ
 //	for _, value := range data.Tasks {
 // 		fmt.Printf("%v\n", value)
 // 	}
-func (c *Client) Tasks(parameters TasksRequest) (TasksResponse, int, errs.Failure) {
+func (c *Client) Tasks(parameters TasksRequest) (TasksResponse, int, *errs.Failure) {
 	var resp TasksResponse
 
 	params, _ := query.Values(parameters)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/tasks?%s", params.Encode()))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // TaskCreate create a task
@@ -3215,7 +3291,7 @@ func (c *Client) Tasks(parameters TasksRequest) (TasksResponse, int, errs.Failur
 //		PerformerID: 12,
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -3226,7 +3302,7 @@ func (c *Client) Tasks(parameters TasksRequest) (TasksResponse, int, errs.Failur
 //	if data.Success == true {
 // 		fmt.Printf("%v\n", data.ID)
 // 	}
-func (c *Client) TaskCreate(task Task, site ...string) (CreateResponse, int, errs.Failure) {
+func (c *Client) TaskCreate(task Task, site ...string) (CreateResponse, int, *errs.Failure) {
 	var resp CreateResponse
 	taskJSON, _ := json.Marshal(&task)
 
@@ -3237,17 +3313,18 @@ func (c *Client) TaskCreate(task Task, site ...string) (CreateResponse, int, err
 	fillSite(&p, site)
 
 	data, status, err := c.PostRequest("/tasks/create", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Task returns task
@@ -3260,7 +3337,7 @@ func (c *Client) TaskCreate(task Task, site ...string) (CreateResponse, int, err
 //
 // 	data, status, err := client.Task(12)
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -3271,21 +3348,22 @@ func (c *Client) TaskCreate(task Task, site ...string) (CreateResponse, int, err
 //	if data.Success == true {
 // 		fmt.Printf("%v\n", data.Task)
 // 	}
-func (c *Client) Task(id int) (TaskResponse, int, errs.Failure) {
+func (c *Client) Task(id int) (TaskResponse, int, *errs.Failure) {
 	var resp TaskResponse
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/tasks/%d", id))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // TaskEdit edit a task
@@ -3301,14 +3379,14 @@ func (c *Client) Task(id int) (TaskResponse, int, errs.Failure) {
 //		Text: "task №2",
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) TaskEdit(task Task, site ...string) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) TaskEdit(task Task, site ...string) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 	var uid = strconv.Itoa(task.ID)
 
@@ -3321,17 +3399,18 @@ func (c *Client) TaskEdit(task Task, site ...string) (SuccessfulResponse, int, e
 	fillSite(&p, site)
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/tasks/%s/edit", uid), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // UserGroups returns list of user groups
@@ -3344,7 +3423,7 @@ func (c *Client) TaskEdit(task Task, site ...string) (SuccessfulResponse, int, e
 //
 // 	data, status, err := client.UserGroups(v5.UserGroupsRequest{Page: 1})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -3355,23 +3434,24 @@ func (c *Client) TaskEdit(task Task, site ...string) (SuccessfulResponse, int, e
 //	for _, value := range data.Groups {
 // 		fmt.Printf("%v\n", value)
 // 	}
-func (c *Client) UserGroups(parameters UserGroupsRequest) (UserGroupsResponse, int, errs.Failure) {
+func (c *Client) UserGroups(parameters UserGroupsRequest) (UserGroupsResponse, int, *errs.Failure) {
 	var resp UserGroupsResponse
 
 	params, _ := query.Values(parameters)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/user-groups?%s", params.Encode()))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Users returns list of users matched the specified filters
@@ -3384,7 +3464,7 @@ func (c *Client) UserGroups(parameters UserGroupsRequest) (UserGroupsResponse, i
 //
 // 	data, status, err := client.Users(v5.UsersRequest{Filter: v5.UsersFilter{Active: 1}, Page: 1})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -3395,23 +3475,24 @@ func (c *Client) UserGroups(parameters UserGroupsRequest) (UserGroupsResponse, i
 //	for _, value := range data.Users {
 // 		fmt.Printf("%v\n", value)
 // 	}
-func (c *Client) Users(parameters UsersRequest) (UsersResponse, int, errs.Failure) {
+func (c *Client) Users(parameters UsersRequest) (UsersResponse, int, *errs.Failure) {
 	var resp UsersResponse
 
 	params, _ := query.Values(parameters)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/users?%s", params.Encode()))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // User returns information about user
@@ -3424,7 +3505,7 @@ func (c *Client) Users(parameters UsersRequest) (UsersResponse, int, errs.Failur
 //
 // 	data, status, err := client.User(12)
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -3435,21 +3516,22 @@ func (c *Client) Users(parameters UsersRequest) (UsersResponse, int, errs.Failur
 //	if data.Success == true {
 // 		fmt.Printf("%v\n", data.User)
 // 	}
-func (c *Client) User(id int) (UserResponse, int, errs.Failure) {
+func (c *Client) User(id int) (UserResponse, int, *errs.Failure) {
 	var resp UserResponse
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/users/%d", id))
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // UserStatus change user status
@@ -3462,14 +3544,14 @@ func (c *Client) User(id int) (UserResponse, int, errs.Failure) {
 //
 // 	data, status, err := client.UserStatus(12, "busy")
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) UserStatus(id int, status string) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) UserStatus(id int, status string) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	p := url.Values{
@@ -3477,37 +3559,39 @@ func (c *Client) UserStatus(id int, status string) (SuccessfulResponse, int, err
 	}
 
 	data, st, err := c.PostRequest(fmt.Sprintf("/users/%d/status", id), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, st, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, st, buildErr(data)
+		buildErr(data, err)
+		return resp, st, err
 	}
 
-	return resp, st, err
+	return resp, st, nil
 }
 
 // StaticticsUpdate updates statistics
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#get--api-v5-statistic-update
-func (c *Client) StaticticsUpdate() (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) StaticticsUpdate() (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	data, status, err := c.GetRequest("/statistic/update")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
 	if resp.Success == false {
-		return resp, status, buildErr(data)
+		buildErr(data, err)
+		return resp, status, err
 	}
 
-	return resp, status, err
+	return resp, status, nil
 }
 
 // Costs returns costs list
@@ -3525,7 +3609,7 @@ func (c *Client) StaticticsUpdate() (SuccessfulResponse, int, errs.Failure) {
 //		},
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -3536,20 +3620,25 @@ func (c *Client) StaticticsUpdate() (SuccessfulResponse, int, errs.Failure) {
 // 	for _, value := range data.Costs {
 // 		fmt.Printf("%v\n", value.Summ)
 // 	}
-func (c *Client) Costs(costs CostsRequest) (CostsResponse, int, errs.Failure) {
+func (c *Client) Costs(costs CostsRequest) (CostsResponse, int, *errs.Failure) {
 	var resp CostsResponse
 
 	params, _ := query.Values(costs)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/costs?%s", params.Encode()))
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
-	return resp, status, err
+	if resp.Success == false {
+		buildErr(data, err)
+		return resp, status, err
+	}
+
+	return resp, status, nil
 }
 
 // CostCreate create an cost
@@ -3574,7 +3663,7 @@ func (c *Client) Costs(costs CostsRequest) (CostsResponse, int, errs.Failure) {
 //		"store"
 // 	)
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -3585,7 +3674,7 @@ func (c *Client) Costs(costs CostsRequest) (CostsResponse, int, errs.Failure) {
 // 	If data.Success == true {
 // 		fmt.Printf("%v", data.ID)
 // 	}
-func (c *Client) CostCreate(cost CostRecord, site ...string) (CreateResponse, int, errs.Failure) {
+func (c *Client) CostCreate(cost CostRecord, site ...string) (CreateResponse, int, *errs.Failure) {
 	var resp CreateResponse
 
 	costJSON, _ := json.Marshal(&cost)
@@ -3597,13 +3686,18 @@ func (c *Client) CostCreate(cost CostRecord, site ...string) (CreateResponse, in
 	fillSite(&p, site)
 
 	data, status, err := c.PostRequest("/costs/create", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
-	return resp, status, err
+	if resp.Success == false {
+		buildErr(data, err)
+		return resp, status, err
+	}
+
+	return resp, status, nil
 }
 
 // CostsDelete removes a cost
@@ -3616,7 +3710,7 @@ func (c *Client) CostCreate(cost CostRecord, site ...string) (CreateResponse, in
 //
 //	data, status, err := client.client.CostsDelete([]int{1, 2, 3, 48, 49, 50})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -3627,7 +3721,7 @@ func (c *Client) CostCreate(cost CostRecord, site ...string) (CreateResponse, in
 // 	If data.Success == true {
 // 		fmt.Printf("Not removed costs: %v", data.NotRemovedIds)
 // 	}
-func (c *Client) CostsDelete(ids []int) (CostsDeleteResponse, int, errs.Failure) {
+func (c *Client) CostsDelete(ids []int) (CostsDeleteResponse, int, *errs.Failure) {
 	var resp CostsDeleteResponse
 
 	costJSON, _ := json.Marshal(&ids)
@@ -3637,13 +3731,18 @@ func (c *Client) CostsDelete(ids []int) (CostsDeleteResponse, int, errs.Failure)
 	}
 
 	data, status, err := c.PostRequest("/costs/delete", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
-	return resp, status, err
+	if resp.Success == false {
+		buildErr(data, err)
+		return resp, status, err
+	}
+
+	return resp, status, nil
 }
 
 // CostsUpload batch costs upload
@@ -3673,7 +3772,7 @@ func (c *Client) CostsDelete(ids []int) (CostsDeleteResponse, int, errs.Failure)
 //		}
 // 	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -3684,7 +3783,7 @@ func (c *Client) CostsDelete(ids []int) (CostsDeleteResponse, int, errs.Failure)
 // 	If data.Success == true {
 // 		fmt.Printf("Uploaded costs: %v", data.UploadedCosts)
 // 	}
-func (c *Client) CostsUpload(cost []CostRecord) (CostsUploadResponse, int, errs.Failure) {
+func (c *Client) CostsUpload(cost []CostRecord) (CostsUploadResponse, int, *errs.Failure) {
 	var resp CostsUploadResponse
 
 	costJSON, _ := json.Marshal(&cost)
@@ -3694,13 +3793,18 @@ func (c *Client) CostsUpload(cost []CostRecord) (CostsUploadResponse, int, errs.
 	}
 
 	data, status, err := c.PostRequest("/costs/upload", p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
-	return resp, status, err
+	if resp.Success == false {
+		buildErr(data, err)
+		return resp, status, err
+	}
+
+	return resp, status, nil
 }
 
 // Cost returns information about specified cost
@@ -3713,7 +3817,7 @@ func (c *Client) CostsUpload(cost []CostRecord) (CostsUploadResponse, int, errs.
 //
 //	data, status, err := client.Cost(1)
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -3724,18 +3828,23 @@ func (c *Client) CostsUpload(cost []CostRecord) (CostsUploadResponse, int, errs.
 // 	If data.Success == true {
 // 		fmt.Printf("%v", data.Cost)
 // 	}
-func (c *Client) Cost(id int) (CostResponse, int, errs.Failure) {
+func (c *Client) Cost(id int) (CostResponse, int, *errs.Failure) {
 	var resp CostResponse
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/costs/%d", id))
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
-	return resp, status, err
+	if resp.Success == false {
+		buildErr(data, err)
+		return resp, status, err
+	}
+
+	return resp, status, nil
 }
 
 // CostDelete removes cost
@@ -3748,14 +3857,14 @@ func (c *Client) Cost(id int) (CostResponse, int, errs.Failure) {
 //
 //	data, status, err := client.CostDelete(1)
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
 // 	if status >= http.StatusBadRequest {
 // 		fmt.Printf("%v", err.ApiErr())
 // 	}
-func (c *Client) CostDelete(id int) (SuccessfulResponse, int, errs.Failure) {
+func (c *Client) CostDelete(id int) (SuccessfulResponse, int, *errs.Failure) {
 	var resp SuccessfulResponse
 
 	costJSON, _ := json.Marshal(&id)
@@ -3766,13 +3875,18 @@ func (c *Client) CostDelete(id int) (SuccessfulResponse, int, errs.Failure) {
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/costs/%d/delete", id), p)
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
-	return resp, status, err
+	if resp.Success == false {
+		buildErr(data, err)
+		return resp, status, err
+	}
+
+	return resp, status, nil
 }
 
 // CostEdit edit a cost
@@ -3790,7 +3904,7 @@ func (c *Client) CostDelete(id int) (SuccessfulResponse, int, errs.Failure) {
 //		CostItem:  "seo",
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -3801,7 +3915,7 @@ func (c *Client) CostDelete(id int) (SuccessfulResponse, int, errs.Failure) {
 // 	If data.Success == true {
 // 		fmt.Printf("%v", data.Id)
 // 	}
-func (c *Client) CostEdit(id int, cost CostRecord, site ...string) (CreateResponse, int, errs.Failure) {
+func (c *Client) CostEdit(id int, cost CostRecord, site ...string) (CreateResponse, int, *errs.Failure) {
 	var resp CreateResponse
 
 	costJSON, _ := json.Marshal(&cost)
@@ -3813,13 +3927,18 @@ func (c *Client) CostEdit(id int, cost CostRecord, site ...string) (CreateRespon
 	fillSite(&p, site)
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/costs/%d/edit", id), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
-	return resp, status, err
+	if resp.Success == false {
+		buildErr(data, err)
+		return resp, status, err
+	}
+
+	return resp, status, nil
 }
 
 // CustomFields returns list of custom fields
@@ -3835,7 +3954,7 @@ func (c *Client) CostEdit(id int, cost CostRecord, site ...string) (CreateRespon
 // 		Entity: "customer",
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -3846,20 +3965,25 @@ func (c *Client) CostEdit(id int, cost CostRecord, site ...string) (CreateRespon
 // 	for _, value := range data.CustomFields {
 //		fmt.Printf("%v\n", value)
 //	}
-func (c *Client) CustomFields(customFields CustomFieldsRequest) (CustomFieldsResponse, int, errs.Failure) {
+func (c *Client) CustomFields(customFields CustomFieldsRequest) (CustomFieldsResponse, int, *errs.Failure) {
 	var resp CustomFieldsResponse
 
 	params, _ := query.Values(customFields)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/custom-fields?%s", params.Encode()))
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
-	return resp, status, err
+	if resp.Success == false {
+		buildErr(data, err)
+		return resp, status, err
+	}
+
+	return resp, status, nil
 }
 
 // CustomDictionaries returns list of custom directory
@@ -3876,7 +4000,7 @@ func (c *Client) CustomFields(customFields CustomFieldsRequest) (CustomFieldsRes
 //		},
 //	})
 //
-//	if err.RuntimeErr != nil {
+//	if err.Error() != "" {
 //		fmt.Printf("%v", err.RuntimeErr)
 //	}
 //
@@ -3887,20 +4011,25 @@ func (c *Client) CustomFields(customFields CustomFieldsRequest) (CustomFieldsRes
 //	for _, value := range data.CustomDictionaries {
 //		fmt.Printf("%v\n", value.Elements)
 //	}
-func (c *Client) CustomDictionaries(customDictionaries CustomDictionariesRequest) (CustomDictionariesResponse, int, errs.Failure) {
+func (c *Client) CustomDictionaries(customDictionaries CustomDictionariesRequest) (CustomDictionariesResponse, int, *errs.Failure) {
 	var resp CustomDictionariesResponse
 
 	params, _ := query.Values(customDictionaries)
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/custom-fields/dictionaries?%s", params.Encode()))
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
-	return resp, status, err
+	if resp.Success == false {
+		buildErr(data, err)
+		return resp, status, err
+	}
+
+	return resp, status, nil
 }
 
 // CustomDictionariesCreate creates a custom dictionary
@@ -3926,7 +4055,7 @@ func (c *Client) CustomDictionaries(customDictionaries CustomDictionariesRequest
 //		},
 //	})
 //
-//	if err.RuntimeErr != nil {
+//	if err.Error() != "" {
 //		fmt.Printf("%v", err.RuntimeErr)
 //	}
 //
@@ -3937,7 +4066,7 @@ func (c *Client) CustomDictionaries(customDictionaries CustomDictionariesRequest
 //	If data.Success == true {
 //		fmt.Printf("%v", data.Code)
 //	}
-func (c *Client) CustomDictionariesCreate(customDictionary CustomDictionary) (CustomResponse, int, errs.Failure) {
+func (c *Client) CustomDictionariesCreate(customDictionary CustomDictionary) (CustomResponse, int, *errs.Failure) {
 	var resp CustomResponse
 
 	costJSON, _ := json.Marshal(&customDictionary)
@@ -3948,13 +4077,18 @@ func (c *Client) CustomDictionariesCreate(customDictionary CustomDictionary) (Cu
 
 	data, status, err := c.PostRequest("/custom-fields/dictionaries/create", p)
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
-	return resp, status, err
+	if resp.Success == false {
+		buildErr(data, err)
+		return resp, status, err
+	}
+
+	return resp, status, nil
 }
 
 // CustomDictionary returns information about dictionary
@@ -3967,7 +4101,7 @@ func (c *Client) CustomDictionariesCreate(customDictionary CustomDictionary) (Cu
 //
 //	data, status, err := client.CustomDictionary("courier-profiles")
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -3978,18 +4112,23 @@ func (c *Client) CustomDictionariesCreate(customDictionary CustomDictionary) (Cu
 // 	If data.Success == true {
 // 		fmt.Printf("%v", data.CustomDictionary.Name)
 // 	}
-func (c *Client) CustomDictionary(code string) (CustomDictionaryResponse, int, errs.Failure) {
+func (c *Client) CustomDictionary(code string) (CustomDictionaryResponse, int, *errs.Failure) {
 	var resp CustomDictionaryResponse
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/custom-fields/dictionaries/%s", code))
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
-	return resp, status, err
+	if resp.Success == false {
+		buildErr(data, err)
+		return resp, status, err
+	}
+
+	return resp, status, nil
 }
 
 // CustomDictionaryEdit edit custom dictionary
@@ -4015,7 +4154,7 @@ func (c *Client) CustomDictionary(code string) (CustomDictionaryResponse, int, e
 //		},
 //	})
 //
-//	if err.RuntimeErr != nil {
+//	if err.Error() != "" {
 //		fmt.Printf("%v", err.RuntimeErr)
 //	}
 //
@@ -4026,7 +4165,7 @@ func (c *Client) CustomDictionary(code string) (CustomDictionaryResponse, int, e
 //	If data.Success == true {
 //		fmt.Printf("%v", data.Code)
 //	}
-func (c *Client) CustomDictionaryEdit(customDictionary CustomDictionary) (CustomResponse, int, errs.Failure) {
+func (c *Client) CustomDictionaryEdit(customDictionary CustomDictionary) (CustomResponse, int, *errs.Failure) {
 	var resp CustomResponse
 
 	costJSON, _ := json.Marshal(&customDictionary)
@@ -4036,13 +4175,18 @@ func (c *Client) CustomDictionaryEdit(customDictionary CustomDictionary) (Custom
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/custom-fields/dictionaries/%s/edit", customDictionary.Code), p)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
-	return resp, status, err
+	if resp.Success == false {
+		buildErr(data, err)
+		return resp, status, err
+	}
+
+	return resp, status, nil
 }
 
 // CustomFieldsCreate creates custom field
@@ -4061,7 +4205,7 @@ func (c *Client) CustomDictionaryEdit(customDictionary CustomDictionary) (Custom
 //		DisplayArea: "customer",
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -4072,7 +4216,7 @@ func (c *Client) CustomDictionaryEdit(customDictionary CustomDictionary) (Custom
 // 	If data.Success == true {
 // 		fmt.Printf("%v", data.Code)
 // 	}
-func (c *Client) CustomFieldsCreate(customFields CustomFields) (CustomResponse, int, errs.Failure) {
+func (c *Client) CustomFieldsCreate(customFields CustomFields) (CustomResponse, int, *errs.Failure) {
 	var resp CustomResponse
 
 	costJSON, _ := json.Marshal(&customFields)
@@ -4083,13 +4227,18 @@ func (c *Client) CustomFieldsCreate(customFields CustomFields) (CustomResponse,
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/custom-fields/%s/create", customFields.Entity), p)
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
-	return resp, status, err
+	if resp.Success == false {
+		buildErr(data, err)
+		return resp, status, err
+	}
+
+	return resp, status, nil
 }
 
 // CustomField returns information about custom fields
@@ -4102,7 +4251,7 @@ func (c *Client) CustomFieldsCreate(customFields CustomFields) (CustomResponse,
 //
 //	data, status, err := client.CustomField("order", "first-order")
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -4113,18 +4262,23 @@ func (c *Client) CustomFieldsCreate(customFields CustomFields) (CustomResponse,
 // 	If data.Success == true {
 // 		fmt.Printf("%v", data.CustomField)
 // 	}
-func (c *Client) CustomField(entity, code string) (CustomFieldResponse, int, errs.Failure) {
+func (c *Client) CustomField(entity, code string) (CustomFieldResponse, int, *errs.Failure) {
 	var resp CustomFieldResponse
 
 	data, status, err := c.GetRequest(fmt.Sprintf("/custom-fields/%s/%s", entity, code))
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
-	return resp, status, err
+	if resp.Success == false {
+		buildErr(data, err)
+		return resp, status, err
+	}
+
+	return resp, status, nil
 }
 
 // CustomFieldEdit list method
@@ -4141,7 +4295,7 @@ func (c *Client) CustomField(entity, code string) (CustomFieldResponse, int, err
 //		DisplayArea: "delivery",
 //	})
 //
-// 	if err.RuntimeErr != nil {
+// 	if err.Error() != "" {
 // 		fmt.Printf("%v", err.RuntimeErr)
 // 	}
 //
@@ -4152,7 +4306,7 @@ func (c *Client) CustomField(entity, code string) (CustomFieldResponse, int, err
 // 	If data.Success == true {
 // 		fmt.Printf("%v", data.Code)
 // 	}
-func (c *Client) CustomFieldEdit(customFields CustomFields) (CustomResponse, int, errs.Failure) {
+func (c *Client) CustomFieldEdit(customFields CustomFields) (CustomResponse, int, *errs.Failure) {
 	var resp CustomResponse
 
 	costJSON, _ := json.Marshal(&customFields)
@@ -4163,11 +4317,16 @@ func (c *Client) CustomFieldEdit(customFields CustomFields) (CustomResponse, int
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/custom-fields/%s/%s/edit", customFields.Entity, customFields.Code), p)
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		return resp, status, err
 	}
 
 	json.Unmarshal(data, &resp)
 
-	return resp, status, err
+	if resp.Success == false {
+		buildErr(data, err)
+		return resp, status, err
+	}
+
+	return resp, status, nil
 }
diff --git a/v5/client_test.go b/v5/client_test.go
index dbb4301..591ca2d 100644
--- a/v5/client_test.go
+++ b/v5/client_test.go
@@ -65,12 +65,16 @@ func badurlclient() *Client {
 	return New(badURL, os.Getenv("RETAILCRM_KEY"))
 }
 
-func badkeyclient() *Client {
-	return New(os.Getenv("RETAILCRM_URL"), "1234567890")
-}
-
 func TestGetRequest(t *testing.T) {
 	c := client()
+
+	defer gock.Off()
+
+	gock.New(crmURL).
+		Get("/api/v5/fake-method").
+		Reply(404).
+		BodyString(`{"success": false, "errorMsg" : "Method not found"}`)
+
 	_, status, _ := c.GetRequest("/fake-method")
 
 	if status != http.StatusNotFound {
@@ -80,6 +84,14 @@ func TestGetRequest(t *testing.T) {
 
 func TestPostRequest(t *testing.T) {
 	c := client()
+
+	defer gock.Off()
+
+	gock.New(crmURL).
+		Post("/api/v5/fake-method").
+		Reply(404).
+		BodyString(`{"success": false, "errorMsg" : "Method not found"}`)
+
 	_, status, _ := c.PostRequest("/fake-method", url.Values{})
 
 	if status != http.StatusNotFound {
@@ -90,8 +102,15 @@ func TestPostRequest(t *testing.T) {
 func TestClient_ApiVersionsVersions(t *testing.T) {
 	c := client()
 
+	defer gock.Off()
+
+	gock.New(crmURL).
+		Get("/api/api-versions").
+		Reply(200).
+		BodyString(`{"success": true, "versions" : ["1.0", "4.0", "3.0", "4.0", "5.0"]}`)
+
 	data, status, err := c.APIVersions()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -115,7 +134,7 @@ func TestClient_ApiVersionsVersionsBadUrl(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg" : "Account does not exist"}`)
 
 	data, status, err := c.APIVersions()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -136,10 +155,10 @@ func TestClient_ApiCredentialsCredentialsBadKey(t *testing.T) {
 		Reply(403).
 		BodyString(`{"success": false, "errorMsg": "Wrong \"apiKey\" value"}`)
 
-	c := badkeyclient()
+	c := client()
 
 	data, status, err := c.APICredentials()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -163,7 +182,7 @@ func TestClient_ApiCredentialsCredentials(t *testing.T) {
 	c := client()
 
 	data, status, err := c.APICredentials()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -195,7 +214,7 @@ func TestClient_CustomersCustomers(t *testing.T) {
 		Page: 3,
 	})
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -225,7 +244,7 @@ func TestClient_CustomersCustomers_Fail(t *testing.T) {
 		},
 	})
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -270,7 +289,7 @@ func TestClient_CustomerChange(t *testing.T) {
 		BodyString(`{"success": true, "id": 123}`)
 
 	cr, sc, err := c.CustomerCreate(f)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -300,7 +319,7 @@ func TestClient_CustomerChange(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	ed, se, err := c.CustomerEdit(f, "id")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -319,7 +338,7 @@ func TestClient_CustomerChange(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, status, err := c.Customer(f.ExternalID, "externalId", "")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -355,7 +374,7 @@ func TestClient_CustomerChange_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Parameter 'externalId' in 'customer' is missing"}`)
 
 	cr, sc, err := c.CustomerCreate(f)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -385,7 +404,7 @@ func TestClient_CustomerChange_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Not found"}`)
 
 	ed, se, err := c.CustomerEdit(f, "id")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -404,7 +423,7 @@ func TestClient_CustomerChange_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Not found"}`)
 
 	data, status, err := c.Customer(codeFail, "externalId", "")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -446,7 +465,7 @@ func TestClient_CustomersUpload(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, status, err := c.CustomersUpload(customers)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -479,7 +498,7 @@ func TestClient_CustomersUpload_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Customers are loaded with errors"}`)
 
 	data, status, err := c.CustomersUpload(customers)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -516,7 +535,7 @@ func TestClient_CustomersCombine(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, status, err := c.CustomersCombine(customers, resultCustomer)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -553,7 +572,7 @@ func TestClient_CustomersCombine_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Invalid input parameters"}`)
 
 	data, status, err := c.CustomersCombine([]Customer{{}, {}}, Customer{})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -590,7 +609,7 @@ func TestClient_CustomersFixExternalIds(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	fx, fe, err := c.CustomersFixExternalIds(customers)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -624,7 +643,7 @@ func TestClient_CustomersFixExternalIds_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"id": "ID must be an integer"}}`)
 
 	data, status, err := c.CustomersFixExternalIds(customers)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -653,7 +672,7 @@ func TestClient_CustomersHistory(t *testing.T) {
 		BodyString(`{"success": true, "history": [{"id": 1}]}`)
 
 	data, status, err := c.CustomersHistory(f)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -687,7 +706,7 @@ func TestClient_CustomersHistory_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"children[startDate]": "Значение недопустимо."}}`)
 
 	data, status, err := c.CustomersHistory(f)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -712,7 +731,7 @@ func TestClient_NotesNotes(t *testing.T) {
 		BodyString(`{"success": true, "notes": [{"id": 1}]}`)
 
 	data, status, err := c.CustomerNotes(NotesRequest{Page: 1})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -743,7 +762,7 @@ func TestClient_NotesNotes_Fail(t *testing.T) {
 	data, status, err := c.CustomerNotes(NotesRequest{
 		Filter: NotesFilter{CreatedAtFrom: "2020-13-12"},
 	})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -783,7 +802,7 @@ func TestClient_NotesCreateDelete(t *testing.T) {
 		BodyString(`{"success": true, "id": 1}`)
 
 	noteCreateResponse, noteCreateStatus, err := c.CustomerNoteCreate(note)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -807,7 +826,7 @@ func TestClient_NotesCreateDelete(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	noteDeleteResponse, noteDeleteStatus, err := c.CustomerNoteDelete(noteCreateResponse.ID)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -845,7 +864,7 @@ func TestClient_NotesCreateDelete_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the entity format", "errors": {"customer": "Set one of the following fields: id, externalId"}}`)
 
 	data, status, err := c.CustomerNoteCreate(note)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -869,7 +888,7 @@ func TestClient_NotesCreateDelete_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Note not found map"}`)
 
 	noteDeleteResponse, noteDeleteStatus, err := c.CustomerNoteDelete(iCodeFail)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -895,7 +914,7 @@ func TestClient_OrdersOrders(t *testing.T) {
 		BodyString(`{"success": true, "orders":  [{"id": 1}]}`)
 
 	data, status, err := c.Orders(OrdersRequest{Filter: OrdersFilter{City: "Москва"}, Page: 1})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -921,7 +940,7 @@ func TestClient_OrdersOrders_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"children[attachments]": "SThis value is not valid."}}`)
 
 	data, status, err := c.Orders(OrdersRequest{Filter: OrdersFilter{Attachments: 7}})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -963,7 +982,7 @@ func TestClient_OrderChange(t *testing.T) {
 		BodyString(`{"success": true, "id": 1}`)
 
 	cr, sc, err := c.OrderCreate(f)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -993,7 +1012,7 @@ func TestClient_OrderChange(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	ed, se, err := c.OrderEdit(f, "id")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1012,7 +1031,7 @@ func TestClient_OrderChange(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, status, err := c.Order(f.ExternalID, "externalId", "")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1056,7 +1075,7 @@ func TestClient_OrderChange_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Not found map"}`)
 
 	data, status, err := c.OrderEdit(f, "id")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1098,7 +1117,7 @@ func TestClient_OrdersUpload(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, status, err := c.OrdersUpload(orders)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1140,7 +1159,7 @@ func TestClient_OrdersUpload_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Orders are loaded with errors"}`)
 
 	data, status, err := c.OrdersUpload(orders)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1174,7 +1193,7 @@ func TestClient_OrdersCombine(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, status, err := c.OrdersCombine("ours", Order{ID: 1}, Order{ID: 2})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1208,7 +1227,7 @@ func TestClient_OrdersCombine_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Invalid input parameters"}`)
 
 	data, status, err := c.OrdersCombine("ours", Order{}, Order{})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1244,7 +1263,7 @@ func TestClient_OrdersFixExternalIds(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	fx, fe, err := c.OrdersFixExternalIds(orders)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1277,7 +1296,7 @@ func TestClient_OrdersFixExternalIds_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Invalid input parameters"}`)
 
 	data, status, err := c.OrdersFixExternalIds(orders)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1302,7 +1321,7 @@ func TestClient_OrdersHistory(t *testing.T) {
 		BodyString(`{"success": true, "history": [{"id": 1}]}`)
 
 	data, status, err := c.OrdersHistory(OrdersHistoryRequest{Filter: OrdersHistoryFilter{SinceID: 20}})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1332,7 +1351,7 @@ func TestClient_OrdersHistory_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"children[startDate]": "Значение недопустимо."}}`)
 
 	data, status, err := c.OrdersHistory(OrdersHistoryRequest{Filter: OrdersHistoryFilter{StartDate: "2020-13-12"}})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1371,7 +1390,7 @@ func TestClient_PaymentCreateEditDelete(t *testing.T) {
 		BodyString(`{"success": true, "id": 1}`)
 
 	paymentCreateResponse, status, err := c.OrderPaymentCreate(f)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1401,7 +1420,7 @@ func TestClient_PaymentCreateEditDelete(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	paymentEditResponse, status, err := c.OrderPaymentEdit(k, "id")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1425,7 +1444,7 @@ func TestClient_PaymentCreateEditDelete(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	paymentDeleteResponse, status, err := c.OrderPaymentDelete(paymentCreateResponse.ID)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1462,7 +1481,7 @@ func TestClient_PaymentCreateEditDelete_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the entity format", "errors": {"order": "Set one of the following fields: id, externalId, number"}}`)
 
 	data, status, err := c.OrderPaymentCreate(f)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1492,7 +1511,7 @@ func TestClient_PaymentCreateEditDelete_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Payment not found"}`)
 
 	paymentEditResponse, status, err := c.OrderPaymentEdit(k, "id")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1516,7 +1535,7 @@ func TestClient_PaymentCreateEditDelete_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Payment not found"}`)
 
 	paymentDeleteResponse, status, err := c.OrderPaymentDelete(iCodeFail)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1548,7 +1567,7 @@ func TestClient_TasksTasks(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, status, err := c.Tasks(f)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1578,7 +1597,7 @@ func TestClient_TasksTasks_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters"}`)
 
 	data, status, err := c.Tasks(f)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1613,7 +1632,7 @@ func TestClient_TaskChange(t *testing.T) {
 		BodyString(`{"success": true, "id": 1}`)
 
 	cr, sc, err := c.TaskCreate(f)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1634,7 +1653,7 @@ func TestClient_TaskChange(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	gt, sg, err := c.Task(f.ID)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1659,7 +1678,7 @@ func TestClient_TaskChange(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, status, err := c.TaskEdit(f)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1696,7 +1715,7 @@ func TestClient_TaskChange_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Task is not loaded", "errors": {"performerId": "This value should not be blank."}}`)
 
 	data, status, err := c.TaskEdit(f)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1722,7 +1741,7 @@ func TestClient_UsersUsers(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, status, err := c.Users(UsersRequest{Filter: UsersFilter{Active: 1}, Page: 1})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1749,7 +1768,7 @@ func TestClient_UsersUsers_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"active": "he value you selected is not a valid choice."}}`)
 
 	data, status, err := c.Users(UsersRequest{Filter: UsersFilter{Active: 3}, Page: 1})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1773,7 +1792,7 @@ func TestClient_UsersUser(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.User(user)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1798,7 +1817,7 @@ func TestClient_UsersUser_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Not found"}`)
 
 	data, status, err := c.User(iCodeFail)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1823,7 +1842,7 @@ func TestClient_UsersGroups(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, status, err := c.UserGroups(UserGroupsRequest{Page: 1})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1853,7 +1872,7 @@ func TestClient_UsersUpdate(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.UserStatus(user, "busy")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1884,7 +1903,7 @@ func TestClient_UsersUpdate_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Not found"}`)
 
 	data, status, err := c.UserStatus(iCodeFail, "busy")
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1908,7 +1927,7 @@ func TestClient_StaticticsUpdate(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.StaticticsUpdate()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1932,7 +1951,7 @@ func TestClient_Countries(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.Couriers()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1956,7 +1975,7 @@ func TestClient_CostGroups(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.CostGroups()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -1980,7 +1999,7 @@ func TestClient_CostItems(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.CostItems()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2004,7 +2023,7 @@ func TestClient_Couriers(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.Couriers()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2028,7 +2047,7 @@ func TestClient_DeliveryService(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.DeliveryServices()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2052,7 +2071,7 @@ func TestClient_DeliveryTypes(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.DeliveryTypes()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2076,7 +2095,7 @@ func TestClient_LegalEntities(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.LegalEntities()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2100,7 +2119,7 @@ func TestClient_OrderMethods(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.OrderMethods()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2124,7 +2143,7 @@ func TestClient_OrderTypes(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.OrderTypes()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2148,7 +2167,7 @@ func TestClient_PaymentStatuses(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.PaymentStatuses()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2172,7 +2191,7 @@ func TestClient_PaymentTypes(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.PaymentTypes()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2196,7 +2215,7 @@ func TestClient_PriceTypes(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.PriceTypes()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2220,7 +2239,7 @@ func TestClient_ProductStatuses(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.ProductStatuses()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2244,7 +2263,7 @@ func TestClient_Statuses(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.Statuses()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2268,7 +2287,7 @@ func TestClient_StatusGroups(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.StatusGroups()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2292,7 +2311,7 @@ func TestClient_Sites(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.Sites()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2316,7 +2335,7 @@ func TestClient_Stores(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.Stores()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2357,7 +2376,7 @@ func TestClient_CostGroupItemEdit(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.CostGroupEdit(costGroup)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2392,7 +2411,7 @@ func TestClient_CostGroupItemEdit(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	idata, st, err := c.CostItemEdit(costItem)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2432,7 +2451,7 @@ func TestClient_CostGroupItemEdit_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters"}`)
 
 	data, status, err := c.CostGroupEdit(costGroup)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2467,7 +2486,7 @@ func TestClient_CostGroupItemEdit_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters"}`)
 
 	idata, st, err := c.CostItemEdit(costItem)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2506,7 +2525,7 @@ func TestClient_Courier(t *testing.T) {
 		BodyString(`{"success": true, "id": 1}`)
 
 	data, st, err := c.CourierCreate(cur)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2535,7 +2554,7 @@ func TestClient_Courier(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	idata, st, err := c.CourierEdit(cur)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2568,7 +2587,7 @@ func TestClient_Courier_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the entity format", "errors": {"firstName": "Specify the first name"}}`)
 
 	data, st, err := c.CourierCreate(Courier{})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2595,7 +2614,7 @@ func TestClient_Courier_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "An attempt was made to edit a nonexistent record"}`)
 
 	idata, st, err := c.CourierEdit(cur)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2633,7 +2652,7 @@ func TestClient_DeliveryServiceEdit(t *testing.T) {
 		BodyString(`{"success": true, "id": 1}`)
 
 	data, st, err := c.DeliveryServiceEdit(deliveryService)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2670,7 +2689,7 @@ func TestClient_DeliveryServiceEdit_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "API method not found"}`)
 
 	data, st, err := c.DeliveryServiceEdit(deliveryService)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2713,7 +2732,7 @@ func TestClient_DeliveryTypeEdit(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.DeliveryTypeEdit(deliveryType)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2754,7 +2773,7 @@ func TestClient_DeliveryTypeEdit_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "API method not found"}`)
 
 	data, st, err := c.DeliveryTypeEdit(deliveryType)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2792,7 +2811,7 @@ func TestClient_OrderMethodEdit(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.OrderMethodEdit(orderMethod)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2830,7 +2849,7 @@ func TestClient_OrderMethodEdit_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "API method not found"}`)
 
 	data, st, err := c.OrderMethodEdit(orderMethod)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2869,7 +2888,7 @@ func TestClient_OrderTypeEdit(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.OrderTypeEdit(orderType)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2906,7 +2925,7 @@ func TestClient_OrderTypeEdit_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "API method not found"}`)
 
 	data, st, err := c.OrderTypeEdit(orderType)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2947,7 +2966,7 @@ func TestClient_PaymentStatusEdit(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.PaymentStatusEdit(paymentStatus)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -2987,7 +3006,7 @@ func TestClient_PaymentStatusEdit_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "API method not found"}`)
 
 	data, st, err := c.PaymentStatusEdit(paymentStatus)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3025,7 +3044,7 @@ func TestClient_PaymentTypeEdit(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.PaymentTypeEdit(paymentType)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3063,7 +3082,7 @@ func TestClient_PaymentTypeEdit_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "API method not found"}`)
 
 	data, st, err := c.PaymentTypeEdit(paymentType)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3100,7 +3119,7 @@ func TestClient_PriceTypeEdit(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.PriceTypeEdit(priceType)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3136,7 +3155,7 @@ func TestClient_PriceTypeEdit_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "API method not found"}`)
 
 	data, st, err := c.PriceTypeEdit(priceType)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3174,7 +3193,7 @@ func TestClient_ProductStatusEdit(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.ProductStatusEdit(productStatus)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3211,7 +3230,7 @@ func TestClient_ProductStatusEdit_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "API method not found"}`)
 
 	data, st, err := c.ProductStatusEdit(productStatus)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3249,7 +3268,7 @@ func TestClient_StatusEdit(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.StatusEdit(status)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3288,7 +3307,7 @@ func TestClient_StatusEdit_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "API method not found"}`)
 
 	data, st, err := c.StatusEdit(status)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3326,7 +3345,7 @@ func TestClient_SiteEdit(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, _, err := c.SiteEdit(site)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3360,7 +3379,7 @@ func TestClient_SiteEdit_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Method Not Allowed"}`)
 
 	data, _, err := c.SiteEdit(site)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3396,7 +3415,7 @@ func TestClient_StoreEdit(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.StoreEdit(store)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3435,7 +3454,7 @@ func TestClient_StoreEdit_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "API method not found"}`)
 
 	data, st, err := c.StoreEdit(store)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3459,7 +3478,7 @@ func TestClient_Units(t *testing.T) {
 		BodyString(`{"success": true, "units": []}`)
 
 	data, st, err := c.Units()
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3478,11 +3497,11 @@ func TestClient_UnitsEdit(t *testing.T) {
 	defer gock.Off()
 
 	unit := Unit{
-		Code:          RandomString(5),
-		Name:          RandomString(5),
-		Sym:           RandomString(2),
-		Default:       false,
-		Active:        true,
+		Code:    RandomString(5),
+		Name:    RandomString(5),
+		Sym:     RandomString(2),
+		Default: false,
+		Active:  true,
 	}
 
 	jr, _ := json.Marshal(&unit)
@@ -3499,7 +3518,7 @@ func TestClient_UnitsEdit(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, st, err := c.UnitEdit(unit)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3518,14 +3537,14 @@ func TestClient_UnitEdit_Fail(t *testing.T) {
 	defer gock.Off()
 
 	unit := Unit{
-		Name:          RandomString(5),
-		Active:        false,
+		Name:   RandomString(5),
+		Active: false,
 	}
 
 	jr, _ := json.Marshal(&unit)
 
 	p := url.Values{
-		"store": {string(jr[:])},
+		"unit": {string(jr[:])},
 	}
 
 	gock.New(crmURL).
@@ -3533,10 +3552,10 @@ func TestClient_UnitEdit_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(404).
-		BodyString(`{"success": false, "errorMsg": "API method not found"}`)
+		BodyString(`{"success": false, "errorMsg": "Method not found"}`)
 
 	data, st, err := c.UnitEdit(unit)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3573,7 +3592,7 @@ func TestClient_PackChange(t *testing.T) {
 		BodyString(`{"success": true, "id": 1}`)
 
 	p, status, err := c.PackCreate(pack)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3591,7 +3610,7 @@ func TestClient_PackChange(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	s, status, err := c.Pack(p.ID)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3617,7 +3636,7 @@ func TestClient_PackChange(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	e, status, err := c.PackEdit(Pack{ID: p.ID, Quantity: 2})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3636,7 +3655,7 @@ func TestClient_PackChange(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	d, status, err := c.PackDelete(p.ID)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3674,7 +3693,7 @@ func TestClient_PackChange_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the entity format"}`)
 
 	p, status, err := c.PackCreate(pack)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3692,7 +3711,7 @@ func TestClient_PackChange_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the entity format"}`)
 
 	s, status, err := c.Pack(iCodeFail)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3718,7 +3737,7 @@ func TestClient_PackChange_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Pack with id 123123 not found"}`)
 
 	e, status, err := c.PackEdit(Pack{ID: iCodeFail, Quantity: 2})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3737,7 +3756,7 @@ func TestClient_PackChange_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Pack not found"}`)
 
 	d, status, err := c.PackDelete(iCodeFail)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3762,7 +3781,7 @@ func TestClient_PacksHistory(t *testing.T) {
 		BodyString(`{"success": true, "history": [{"id": 1}]}`)
 
 	data, status, err := c.PacksHistory(PacksHistoryRequest{Filter: OrdersHistoryFilter{SinceID: 5}})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3792,7 +3811,7 @@ func TestClient_PacksHistory_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters"}`)
 
 	data, status, err := c.PacksHistory(PacksHistoryRequest{Filter: OrdersHistoryFilter{StartDate: "2020-13-12"}})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3817,7 +3836,7 @@ func TestClient_Packs(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	data, status, err := c.Packs(PacksRequest{Filter: PacksFilter{}, Page: 1})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3843,7 +3862,7 @@ func TestClient_Packs_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters"}`)
 
 	data, status, err := c.Packs(PacksRequest{Filter: PacksFilter{ShipmentDateFrom: "2020-13-12"}})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3869,7 +3888,7 @@ func TestClient_Inventories(t *testing.T) {
 		BodyString(`{"success": true, "id": 1}`)
 
 	data, status, err := c.Inventories(InventoriesRequest{Filter: InventoriesFilter{Details: 1}, Page: 1})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3895,7 +3914,7 @@ func TestClient_Inventories_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters"}`)
 
 	data, status, err := c.Inventories(InventoriesRequest{Filter: InventoriesFilter{Sites: []string{codeFail}}})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3919,7 +3938,7 @@ func TestClient_Segments(t *testing.T) {
 		BodyString(`{"success": true, "id": 1}`)
 
 	data, status, err := c.Segments(SegmentsRequest{})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3945,7 +3964,7 @@ func TestClient_Segments_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters"}`)
 
 	data, status, err := c.Segments(SegmentsRequest{Filter: SegmentsFilter{Active: 3}})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -3991,7 +4010,7 @@ func TestClient_IntegrationModule(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	m, status, err := c.IntegrationModuleEdit(integrationModule)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4009,7 +4028,7 @@ func TestClient_IntegrationModule(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	g, status, err := c.IntegrationModule(code)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4054,7 +4073,7 @@ func TestClient_IntegrationModule_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "API method not found"}`)
 
 	m, status, err := c.IntegrationModuleEdit(integrationModule)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4072,7 +4091,7 @@ func TestClient_IntegrationModule_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters"}`)
 
 	g, status, err := c.IntegrationModule(code)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4101,7 +4120,7 @@ func TestClient_ProductsGroup(t *testing.T) {
 			Active: 1,
 		},
 	})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4131,7 +4150,7 @@ func TestClient_ProductsGroup_Fail(t *testing.T) {
 			Active: 3,
 		},
 	})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4162,7 +4181,7 @@ func TestClient_Products(t *testing.T) {
 			MinPrice: 1,
 		},
 	})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4190,7 +4209,7 @@ func TestClient_Products_Fail(t *testing.T) {
 	g, status, err := c.Products(ProductsRequest{
 		Filter: ProductsFilter{Active: 3},
 	})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4222,7 +4241,7 @@ func TestClient_ProductsProperties(t *testing.T) {
 			Sites: sites,
 		},
 	})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4251,7 +4270,7 @@ func TestClient_DeliveryShipments(t *testing.T) {
 			DateFrom: "2017-10-10",
 		},
 	})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4280,7 +4299,7 @@ func TestClient_DeliveryShipments_Fail(t *testing.T) {
 			Stores: []string{codeFail},
 		},
 	})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4320,7 +4339,7 @@ func TestClient_Cost(t *testing.T) {
 
 	data, status, err := c.CostCreate(costRecord)
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4350,7 +4369,7 @@ func TestClient_Cost(t *testing.T) {
 		Page:  1,
 	})
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4369,7 +4388,7 @@ func TestClient_Cost(t *testing.T) {
 
 	cost, status, err := c.Cost(id)
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4400,7 +4419,7 @@ func TestClient_Cost(t *testing.T) {
 
 	costEdit, status, err := c.CostEdit(id, costRecord)
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4427,7 +4446,7 @@ func TestClient_Cost(t *testing.T) {
 
 	costDelete, status, err := c.CostDelete(id)
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4466,7 +4485,7 @@ func TestClient_Cost_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Cost is not loaded"}`)
 
 	data, status, err := c.CostCreate(costRecord)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4474,7 +4493,7 @@ func TestClient_Cost_Fail(t *testing.T) {
 		t.Error(statusFail)
 	}
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4489,7 +4508,7 @@ func TestClient_Cost_Fail(t *testing.T) {
 	costs, status, err := c.Costs(CostsRequest{
 		Filter: CostsFilter{Sites: []string{codeFail}},
 	})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4507,7 +4526,7 @@ func TestClient_Cost_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Not found"}`)
 
 	cost, status, err := c.Cost(id)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4538,7 +4557,7 @@ func TestClient_Cost_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Cost is not loaded"}`)
 
 	costEdit, status, err := c.CostEdit(id, costRecord)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4563,7 +4582,7 @@ func TestClient_Cost_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Not found"}`)
 
 	costDelete, status, err := c.CostDelete(id)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4616,7 +4635,7 @@ func TestClient_CostsUpload(t *testing.T) {
 
 	data, status, err := c.CostsUpload(costsUpload)
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4645,7 +4664,7 @@ func TestClient_CostsUpload(t *testing.T) {
 		BodyString(`{"success": true}`)
 
 	costsDelete, status, err := c.CostsDelete(ids)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4690,7 +4709,7 @@ func TestClient_CostsUpload_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Costs are loaded with errors"}`)
 
 	data, status, err := c.CostsUpload(costsUpload)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4718,7 +4737,7 @@ func TestClient_CostsUpload_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Expected array, but got NULL: null"}`)
 
 	costsDelete, status, err := c.CostsDelete(ids)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4743,7 +4762,7 @@ func TestClient_CustomFields(t *testing.T) {
 
 	data, status, err := c.CustomFields(CustomFieldsRequest{})
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4768,7 +4787,7 @@ func TestClient_CustomFields_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters"}`)
 
 	data, status, err := c.CustomFields(CustomFieldsRequest{Filter: CustomFieldsFilter{Type: codeFail}})
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4814,7 +4833,7 @@ func TestClient_CustomDictionariesCreate(t *testing.T) {
 
 	data, status, err := c.CustomDictionariesCreate(customDictionary)
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4842,7 +4861,7 @@ func TestClient_CustomDictionariesCreate(t *testing.T) {
 		Page:  1,
 	})
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4862,7 +4881,7 @@ func TestClient_CustomDictionariesCreate(t *testing.T) {
 
 	cd, status, err := c.CustomDictionary(code)
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4893,7 +4912,7 @@ func TestClient_CustomDictionariesCreate(t *testing.T) {
 
 	cde, status, err := c.CustomDictionaryEdit(customDictionary)
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4936,7 +4955,7 @@ func TestClient_CustomDictionariesCreate_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters"}`)
 
 	data, status, err := c.CustomDictionariesCreate(customDictionary)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4950,7 +4969,7 @@ func TestClient_CustomDictionariesCreate_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Not found"}`)
 
 	cd, status, err := c.CustomDictionary(codeFail)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -4979,7 +4998,7 @@ func TestClient_CustomDictionariesCreate_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "API method not found"}`)
 
 	cde, status, err := c.CustomDictionaryEdit(customDictionary)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -5021,7 +5040,7 @@ func TestClient_CustomFieldsCreate(t *testing.T) {
 
 	data, status, err := c.CustomFieldsCreate(customFields)
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -5041,7 +5060,7 @@ func TestClient_CustomFieldsCreate(t *testing.T) {
 
 	customField, status, err := c.CustomField("order", codeCustomField)
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -5070,7 +5089,7 @@ func TestClient_CustomFieldsCreate(t *testing.T) {
 
 	customFieldEdit, status, err := c.CustomFieldEdit(customFields)
 
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -5111,7 +5130,7 @@ func TestClient_CustomFieldsCreate_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters"}`)
 
 	data, status, err := c.CustomFieldsCreate(customFields)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -5129,7 +5148,7 @@ func TestClient_CustomFieldsCreate_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "Not found"}`)
 
 	customField, status, err := c.CustomField("order", codeCustomField)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}
 
@@ -5157,7 +5176,7 @@ func TestClient_CustomFieldsCreate_Fail(t *testing.T) {
 		BodyString(`{"success": false, "errorMsg": "API method not found"}`)
 
 	customFieldEdit, status, err := c.CustomFieldEdit(customFields)
-	if err.RuntimeErr != nil {
+	if err.Error() != "" {
 		t.Errorf("%v", err.Error())
 	}