Fix for some error messages that were split into several messages

The exception handler expects the error to be a list on line 33. In my
case they were a string, which lead to the split of the string into
multiple errors containing one character

Author: schtibe

rest_framework_json_api/exceptions.py

@@ -30,7 +30,16 @@ def exception_handler(exc, context):
             if isinstance(error, dict):
                 errors.append(error)
             else:
-                for message in error:
+                if isinstance(error, list):
+                    for message in error:
+                        errors.append({
+                            'detail': message,
+                            'source': {
+                                'pointer': pointer,
+                            },
+                            'status': encoding.force_text(response.status_code),
+                        })
+                else:
                     errors.append({
                         'detail': message,
                         'source': {
@@ -39,6 +48,7 @@ def exception_handler(exc, context):
                         'status': encoding.force_text(response.status_code),
                     })
 
+
     context['view'].resource_name = 'errors'
     response.data = errors
     return response