'Pre or Re-auth stuff...
Args:
http: An \'Http\' object from httplib2.
saw_error: If the user has already tried to contact the server.
If they have, it\'s OK to prompt them. If not, we should not be asking
them for auth info--it\'s possible it\'ll suceed w/o auth.'

def _Authenticate(self, http, saw_error):

    raise NotImplementedError()
