Ticket #13834: natural_key_assertion.diff

django/core/serializers/python.py

@@ -49 +49 @@
         if related is not None:
             if self.use_natural_keys and hasattr(related, 'natural_key'):
                 related = related.natural_key()
+                assert isinstance(related, tuple), \
+                        'natural_key methods should always return a tuple'
             else:
                 if field.rel.field_name == related._meta.pk.name:
                     # Related to remote object via primary key