      "pub_date": "2006-06-16T11:00:00",
      "categories": [
        %(first_category_pk)s,
        %(second_category_pk)s
      ]
    }
  }
  ]
  """
  
 
</s> remove     pass
 </s> add     @classmethod
    def WithData(cls, original_exc, model, fk, field_value):
        """
        Factory method for creating a deserialization error which has a more
        explanatory messsage.
        """
        return cls("%s: (%s:pk=%s) field_value was '%s'" % (original_exc, model, fk, field_value))
    ],
    "meta_data": []
      "pub_date": "2006-06-16T11:00:00",
      "categories": [
        %(first_category_pk)s,
        %(second_category_pk)s
    ],
    "meta_data": []
    }
  }
  ]
  """
  
keep keep keep keep replace keep keep keep keep keep
 Fixed #19820 -- Added more helpful error messages to Python deserializer. 
tests/serializers/tests.py