Class C_with_slots

Lib/test/test_descr.py:4284–4285

        self.assertEqual(repr(b), '<A>')

        class C_with_slots(A_with_slots):
            __slots__ = ()
        c = C_with_slots()
        with self.assertRaisesRegex(TypeError, 'layout differs'):
            C_with_slots.__bases__ = (A_with_slots_dict,)