def test_serverError(self):
        """
        Test the L{ServerError} error: when the server sends a B{SERVER_ERROR}
        token, the originating command fails with L{ServerError}, and the error
        contains the text sent by the server.
        """
        a = b"eggspamm"
        d = self.proto.set(b"foo", a)
        self.assertEqual(self.transport.value(),
                         b"set foo 0 0 8\r\neggspamm\r\n")
        self.assertFailure(d, ServerError)

        def check(err):
            self.assertEqual(str(err), repr(b"zomg"))

        d.addCallback(check)
        self.proto.dataReceived(b"SERVER_ERROR zomg\r\n")
        return d

        Test the L{ServerError} error: when the server sends a B{SERVER_ERROR}
        token, the originating command fails with L{ServerError}, and the error
        contains the text sent by the server.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_memcache.py