Class B_with_slots_dict

Lib/test/test_descr.py:4260–4261

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

        class B_with_slots_dict:
            __slots__ = ('x', '__dict__')
        b = B_with_slots_dict()
        with self.assertRaisesRegex(TypeError, 'layout differs'):
            B_with_slots_dict.__bases__ = (A_with_dict_weakref,)