Improve ErrorType

Marks some fields as required and non null, it also prevents to do useless checks on the frontend if using a typed language.

Author: patrick91

graphene_django/rest_framework/types.py

@@ -3,8 +3,8 @@
 
 
 class ErrorType(graphene.ObjectType):
-    field = graphene.String()
-    messages = graphene.List(graphene.String)
+    field = graphene.String(required=True)
+    messages = graphene.List(graphene.NonNull(graphene.String), required=True)
 
 
 class DictType(UnmountedType):