          Custom manager method is only available on the manager and not on
          querysets.
          """
          Person.custom_queryset_custom_manager.manager_only()
          with self.assertRaises(AttributeError):
              Person.custom_queryset_custom_manager.all().manager_only()
  
      def test_queryset_and_manager(self):
          """
          Queryset method doesn't override the custom manager method.
 
</s> remove                 with self.assertRaises(AttributeError):
 </s> add                 msg = "%r object has no attribute 'optout_public_method'" % manager.__class__.__name__
                with self.assertRaisesMessage(AttributeError, msg): </s> remove         with self.assertRaises(AttributeError):
 </s> add         msg = "type object 'Book' has no attribute 'objects'"
        with self.assertRaisesMessage(AttributeError, msg): </s> remove         with self.assertRaises(AssertionError):
 </s> add         msg = 'Cannot update a query once a slice has been taken.'
        with self.assertRaisesMessage(AssertionError, msg): </s> remove         with self.assertRaises(AttributeError):
 </s> add         with self.assertRaisesMessage(AttributeError, "'Employee' object has no attribute 'id'"): </s> remove         with self.assertRaises(FieldError):
 </s> add         msg = "Unsupported lookup 'blahblah' for CharField or join on the field not permitted."
        with self.assertRaisesMessage(FieldError, msg):
        msg = "'CustomQuerySet' object has no attribute 'manager_only'"
        with self.assertRaisesMessage(AttributeError, msg):
          Custom manager method is only available on the manager and not on
          querysets.
          """
          Person.custom_queryset_custom_manager.manager_only()
        msg = "'CustomQuerySet' object has no attribute 'manager_only'"
        with self.assertRaisesMessage(AttributeError, msg):
              Person.custom_queryset_custom_manager.all().manager_only()
  
      def test_queryset_and_manager(self):
          """
          Queryset method doesn't override the custom manager method.
keep keep keep keep replace keep keep keep keep keep
 Used assertRaisesMessage() to test Django's error messages. 
tests/custom_managers/tests.py