diff --git a/jupyter/base/values/values.yaml b/jupyter/base/values/values.yaml
index b81a800..788bd48 100644
--- a/jupyter/base/values/values.yaml
+++ b/jupyter/base/values/values.yaml
@@ -163,12 +163,13 @@ hub:
         """
         import json
         import os
+        import tornado.options
         from urllib.parse import urlparse
-
+        from tornado.httpclient import AsyncHTTPClient, HTTPRequest
         from tornado.httpserver import HTTPServer
         from tornado.ioloop import IOLoop
-        from tornado.web import Application, RequestHandler, authenticated
-
+        from tornado.log import app_log
+        from tornado.web import Application, HTTPError, RequestHandler, authenticated
         from jupyterhub.services.auth import HubAuthenticated