give Spawners a handle on the Authenticator

band-aid for spawner-authenticator pairs

jupyterhub/app.py

@@ -711,6 +711,7 @@ class JupyterHub(Application):
             self.log.debug("Loading state for %s from db", user.name)
             user.spawner = spawner = self.spawner_class(
                 user=user, hub=self.hub, config=self.config, db=self.db,
+                authenticator=self.authenticator,
             )
             status = yield spawner.poll()
             if status is None: