Configure build failure conditions

So that contributors receive some automated feedback in case maintainers
are not fast enough.

.scrutinizer.yml

@@ -9,3 +9,16 @@ before_commands:
 tools:
     external_code_coverage:
         timeout: 3600
+
+filter:
+    excluded_paths:
+        - docs
+        - tools
+
+build_failure_conditions:
+    - 'elements.rating(<= C).new.exists'                        # No new classes/methods with a rating of C or worse allowed
+    - 'issues.label("coding-style").new.exists'                 # No new coding style issues allowed
+    - 'issues.severity(>= MAJOR).new.exists'                    # New issues of major or higher severity
+    - 'project.metric_change("scrutinizer.test_coverage", < 0)' # Code Coverage decreased from previous inspection
+    - 'patches.label("Doc Comments").new.exists'                # No new doc comments patches allowed
+    - 'patches.label("Unused Use Statements").new.exists'       # No new unused imports patches allowed