diff --git a/jupyterhub/spawner.py b/jupyterhub/spawner.py
index e0e66fff..94492bf9 100644
--- a/jupyterhub/spawner.py
+++ b/jupyterhub/spawner.py
@@ -10,6 +10,7 @@ import pwd
 import signal
 import sys
 import grp
+import warnings
 from subprocess import Popen
 from tempfile import mkdtemp