def authenticate(self):
     """Authenticate against a v2.0 auth service."""
     if self.url is None:
         raise exceptions.AuthUrlNotGiven()
     auth_url = self.url
     body = {
         "credentials": {
             "username": self.username,
             "key": self.password
         }
     }
     return self._authenticate(auth_url, body, root_key='auth')
 def authenticate(self):
     if self.url is None:
         raise exceptions.AuthUrlNotGiven()
     return self._rax_auth(self.url)