It's a complete guess as I don't really know Python, but if you're getting an authentication error that means the underlying connection is actually working, you're just supplying the wrong credentials to the webservice.
I would try the username in combination with the domain like this:
authCred = (AUTH.zsibasic, 'domain\username', 'password' )
failing that, experiment with the different types of authentication your AUTH library offers, eg:
authCred = (AUTH.zsintlm, 'domain\username', 'password' )