text: Title: Network and config issues when starting jupyterhub
  Body: I have a working jupyterhub installation (based mostly on Andrea Zonca's instructions [https://zonca.github.io/2016/04/jupyterhub-sdsc-cloud.html] and it worked flawlessly for a machine-learning workshop. However, I now want to upgrade to using jupyterlab with my hub, and unfortunately experienced much the same problems as https://github.com/jupyterhub/jupyterhub-deploy-docker/issues/26. I could access jupyterlab from the hub by manually changing the url once I had logged in, but was unable to have it as the default url. Hence I'm trying your docker deployment of the hub :)
  
  My first issue arises with nginx on the host. If I have the service running and I start the hub I get the following error: 
  
  ```
  ERROR: for jupyterhub  Cannot start service hub: driver failed programming external connectivity on endpoint jupyterhub (dd0d984e99ddb8ce10900a489c82f96d42ab9f84e9b4977d874c85f0e0374096): Error starting userland proxy: listen tcp 0.0.0.0:443: bind: address already in use
  
  ERROR: for hub  Cannot start service hub: driver failed programming external connectivity on endpoint jupyterhub (dd0d984e99ddb8ce10900a489c82f96d42ab9f84e9b4977d874c85f0e0374096): Error starting userland proxy: listen tcp 0.0.0.0:443: bind: address already in use
  ERROR: Encountered errors while bringing up the project.
  ```
  
  If I stop nginx, the hub starts with no errors, but the site won't load. The logs do however show an error with the config:
  
  ```
  docker logs jupyterhub
  [E 2017-09-11 02:17:41.976 JupyterHub application:569] Exception while loading config file /srv/jupyterhub/jupyterhub_config.py
      Traceback (most recent call last):
        File "/opt/conda/lib/python3.5/site-packages/traitlets/config/application.py", line 557, in _load_config_files
          config = loader.load_config()
        File "/opt/conda/lib/python3.5/site-packages/traitlets/config/loader.py", line 457, in load_config
          self._read_file_as_dict()
        File "/opt/conda/lib/python3.5/site-packages/traitlets/config/loader.py", line 489, in _read_file_as_dict
          py3compat.execfile(conf_filename, namespace)
        File "/opt/conda/lib/python3.5/site-packages/ipython_genutils/py3compat.py", line 185, in execfile
          exec(compiler(f.read(), fname, 'exec'), glob, loc)
        File "/srv/jupyterhub/jupyterhub_config.py", line 80, in <module>
          name = parts[0]
      IndexError: list index out of range
  
  [I 2017-09-11 02:17:41.980 JupyterHub app:745] Writing cookie_secret to /srv/jupyterhub/jupyterhub_cookie_secret
  [W 2017-09-11 02:17:42.302 JupyterHub app:365]
      Generating CONFIGPROXY_AUTH_TOKEN. Restarting the Hub will require restarting the proxy.
      Set CONFIGPROXY_AUTH_TOKEN env or JupyterHub.proxy_auth_token config to avoid this message.
  
  [W 2017-09-11 02:17:42.336 JupyterHub app:864] No admin users, admin interface will be unavailable.
  [W 2017-09-11 02:17:42.337 JupyterHub app:865] Add any administrative users to `c.Authenticator.admin_users` in config.
  [I 2017-09-11 02:17:42.337 JupyterHub app:892] Not using whitelist. Any authenticated user will be allowed.
  [I 2017-09-11 02:17:42.360 JupyterHub app:1453] Hub API listening on http://127.0.0.1:8081/hub/
  [W 2017-09-11 02:17:42.364 JupyterHub app:1174] Running JupyterHub without SSL.  I hope there is SSL termination happening somewhere else...
  [I 2017-09-11 02:17:42.364 JupyterHub app:1176] Starting proxy @ http://*:8000/
  02:17:42.628 - info: [ConfigProxy] Proxying http://*:8000 to http://127.0.0.1:8081
  02:17:42.633 - info: [ConfigProxy] Proxy API at http://127.0.0.1:8001/api/routes
  [I 2017-09-11 02:17:42.675 JupyterHub app:1485] JupyterHub is now running at http://127.0.0.1:8000/
  ```
  
  So, to me it looks as though the userlist isn't there? When I build the image it says it's copying it, so not sure whats happening.
  
  I'm doing all this on a VM running on Openstack with Ubuntu 16.04, and I'm using Docker version 17.06.1-ce, build 874a737, docker-compose version 1.16.1, build 6d1ac21. I want to use PAM and local user accounts so I commented out references to oauth in the Dockerfile and Makefile (previously I was using the systemuser rather than the singleuser, is this another potential source of problems?).
  
  I plan on trying kubernetes and helm in the future, but having never used either, this seemed like the easiest and quickest way to get what I want. Any advice on how to proceed greatly appreciated.