Used assertRaisesMessage in a couple defer tests.

        self.assertEqual(obj.name, "p1")

    def test_defer_select_related_raises_invalid_query(self):

        # When we defer a field and also select_related it, the query is

        # invalid and raises an exception.

        with self.assertRaises(InvalidQuery):

        msg = (

            'Field Primary.related cannot be both deferred and traversed '

            'using select_related at the same time.'

        )

        with self.assertRaisesMessage(InvalidQuery, msg):

            Primary.objects.defer("related").select_related("related")[0]

    def test_only_select_related_raises_invalid_query(self):

        with self.assertRaises(InvalidQuery):

        msg = (

            'Field Primary.related cannot be both deferred and traversed using '

            'select_related at the same time.'

        )

        with self.assertRaisesMessage(InvalidQuery, msg):

            Primary.objects.only("name").select_related("related")[0]

    def test_defer_foreign_keys_are_deferred_and_not_traversed(self):