def test_handshakeFailure(self):
        """
        L{TLSMemoryBIOProtocol} reports errors in the handshake process to the
        application-level protocol object using its C{connectionLost} method
        and disconnects the underlying transport.
        """
        clientConnectionLost = Deferred()
        clientFactory = ClientFactory()
        clientFactory.protocol = (
            lambda: ConnectionLostNotifyingProtocol(
                clientConnectionLost))

        clientContextFactory = HandshakeCallbackContextFactory()
        wrapperFactory = TLSMemoryBIOFactory(
            clientContextFactory, True, clientFactory)
        sslClientProtocol = wrapperFactory.buildProtocol(None)

        serverConnectionLost = Deferred()
        serverFactory = ServerFactory()
        serverFactory.protocol = (
            lambda: ConnectionLostNotifyingProtocol(
                serverConnectionLost))

        # This context factory rejects any clients which do not present a
        # certificate.
        certificateData = FilePath(certPath).getContent()
        certificate = PrivateCertificate.loadPEM(certificateData)
        serverContextFactory = certificate.options(certificate)
        wrapperFactory = TLSMemoryBIOFactory(
            serverContextFactory, False, serverFactory)
        sslServerProtocol = wrapperFactory.buildProtocol(None)

        connectionDeferred = loopbackAsync(sslServerProtocol, sslClientProtocol)

        def cbConnectionLost(protocol):
            # The connection should close on its own in response to the error
            # induced by the client not supplying the required certificate.
            # After that, check to make sure the protocol's connectionLost was
            # called with the right thing.
            protocol.lostConnectionReason.trap(Error)
        clientConnectionLost.addCallback(cbConnectionLost)
        serverConnectionLost.addCallback(cbConnectionLost)

        # Additionally, the underlying transport should have been told to
        # go away.
        return gatherResults([
                clientConnectionLost, serverConnectionLost,
                connectionDeferred])

        L{TLSMemoryBIOProtocol} reports errors in the handshake process to the
        application-level protocol object using its C{connectionLost} method
        and disconnects the underlying transport.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/protocols/test/test_tls.py