def test_KEX_DH_GEX_REQUEST_OLD_badKexAlg(self):
        """
        Test that if the server receives a KEX_DH_GEX_REQUEST_OLD message
        and the key exchange algorithm is not set, we raise a ConchError.
        """
        self.proto.kexAlg = None
        self.assertRaises(ConchError, self.proto.ssh_KEX_DH_GEX_REQUEST_OLD,
                None)

        Test that if the server receives a KEX_DH_GEX_REQUEST_OLD message
        and the key exchange algorithm is not set, we raise a ConchError.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_transport.py