Bugfix in query.py

lodel/leapi/query.py

                     logger.debug(msg)
         if len(ref_dict) == 0:
             return NameError(   "No field named '%s' in referenced objects %s"
-                                % (ref_field, ref_class.__name__))
+                                % (ref_field,
+                                    ','.join([rc.__name__ for rc in ref_classes])))
         return (fieldname, ref_dict)