def test_unknownFailure(self):
        """
        Test that an exception which is a subclass of L{pb.Error} but not
        known on the client side has its type set properly.
        """
        def failureUnknown(fail):
            self.assertEqual(
                fail.type, b'twisted.spread.test.test_pbfailure.UnknownError')
            return 4310
        return self._testImpl('unknownError', 4310, failureUnknown)

        Test that an exception which is a subclass of L{pb.Error} but not
        known on the client side has its type set properly.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/spread/test/test_pbfailure.py