def test_signDataCallbackErrorHandling(self):
        """
        Assert that L{SSHAgentClient.signData} raises a ConchError
        if we get a response from the server whose opcode doesn't match
        the protocol for data signing requests.
        """
        d = self.client.signData(self.rsaPublic.blob(), b"John Hancock")
        self.pump.flush()
        return self.assertFailure(d, ConchError)

        Assert that L{SSHAgentClient.signData} raises a ConchError
        if we get a response from the server whose opcode doesn't match
        the protocol for data signing requests.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_agent.py