def test_NPNAndALPNNoOverlap(self):
        """
        When the client and server have no overlap of protocols, the connection
        fails.
        """
        clientProtocols = [b'h2', b'http/1.1']
        serverProtocols = [b'spdy/3']
        negotiatedProtocol, lostReason = negotiateProtocol(
            serverProtocols=clientProtocols,
            clientProtocols=serverProtocols,
        )
        self.assertIsNone(negotiatedProtocol)
        self.assertEqual(lostReason.type, SSL.Error)

        When the client and server have no overlap of protocols, the connection
        fails.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_sslverify.py