Add message to NonUniqueResultException

lib/Doctrine/ORM/NonUniqueResultException.php

@@ -27,4 +27,10 @@ namespace Doctrine\ORM;
  */
 class NonUniqueResultException extends UnexpectedResultException
 {
+    const DEFAULT_MESSAGE = 'More than one result was found for query although one row or none was expected.';
+
+    public function __construct(string $message = null)
+    {
+        parent::__construct($message ?? self::DEFAULT_MESSAGE);
+    }
 }