Comment 1 for bug 1547331

No - authenticated() is not supposed to work because the job of authenticating has been removed from the client object.

The idea was to not pre-auth, just do what you want to do and catch an AuthorizationFailure if something goes wrong when auth does happen. If you really need to prompt an auth you can do like session.get_token() which will return you an active token which will prompt auth if there hasn't been one or return you a still valid token if there has.

Is there any reason you must pre-auth? the error for an auth failure is fairly distinctive from others.