Description:

I recently updated jupyterhub (and it's database), the login screen works, but as soon as I actually log in, I get a 500 and in the logs the following stack trace:

[E 2018-06-20 08:48:28.202 JupyterHub web:1591] Uncaught exception GET /hub/user/erich/ (::ffff:131.35.53.156)
HTTPServerRequest(protocol='https', host='nlopc46', method='GET', uri='/hub/user/erich/', version='HTTP/1.1', remote_ip='::ffff:131.35.53.156', headers={'X-Forwarded-Host': 'nlopc46', 'X-Forwarded-Proto': 'https>
Traceback (most recent call last):
File "/usr/lib/python3.6/site-packages/tornado/web.py", line 1512, in _execute
result = yield result
File "<string>", line 6, in _wrap_awaitable
File "/usr/lib/python3.6/site-packages/jupyterhub/handlers/base.py", line 999, in get
await self.spawn_single_user(user)
File "/usr/lib/python3.6/site-packages/jupyterhub/handlers/base.py", line 670, in spawn_single_user
await gen.with_timeout(timedelta(seconds=self.slow_spawn_timeout), finish_spawn_future)
File "<string>", line 3, in __await__
File "/usr/lib/python3.6/site-packages/jupyterhub/handlers/base.py", line 625, in finish_user_spawn
await spawn_future
File "/usr/lib/python3.6/site-packages/jupyterhub/user.py", line 486, in spawn
raise e
File "/usr/lib/python3.6/site-packages/jupyterhub/user.py", line 406, in spawn
url = await gen.with_timeout(timedelta(seconds=spawner.start_timeout), f)
File "<string>", line 3, in __await__
RuntimeError: Task got bad yield: <tornado.concurrent.Future object at 0x7f832d3c1d30>


Additional info:
* package version(s)
jupyterhub 0.9.0-2

Steps to reproduce:
upgrade, update database, restart and log in

I just reverted the update by "pacman -U /var/cache/pacman/pkg/jupyterhub-0.8.1-1-any.pkg.tar.xz", playing back the database backup and restarting - and everything works again.