oauth_client_id error

I'm using batchspawner as described by @zonca but I am having troubles making it to work.
The first issue is with the `JUPYTERHUB_API_TOKEN` environmental variable which is not set. I solved it in the same way @zonca did in https://github.com/zonca/batchspawner/commit/a7449e388e06ae6c0b487d7fef29e53c0eefb305 (as described in https://github.com/jupyterhub/jupyterhub/issues/1081)

However it is now failing with

```
Traceback (most recent call last):
File "/glade/work/ddvento/miniconda3/lib/python3.6/site-packages/traitlets/traitlets.py", line 528, in get
value = obj._trait_values[self.name]
KeyError: 'oauth_client_id'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/glade/work/ddvento/miniconda3/bin/jupyterhub-singleuser", line 6, in
main()
File "/glade/work/ddvento/miniconda3/lib/python3.6/site-packages/jupyterhub/singleuser.py", line 495, in main
return SingleUserNotebookApp.launch_instance(argv)
File "/glade/work/ddvento/miniconda3/lib/python3.6/site-packages/jupyter_core/application.py", line 266, in launch_instance
return super(JupyterApp, cls).launch_instance(argv=argv, **kwargs)
File "/glade/work/ddvento/miniconda3/lib/python3.6/site-packages/traitlets/config/application.py", line 657, in launch_instance
app.initialize(argv)
File "/glade/work/ddvento/miniconda3/lib/python3.6/site-packages/jupyterhub/singleuser.py", line 402, in initialize
return super().initialize(argv)
File "", line 2, in initialize
File "/glade/work/ddvento/miniconda3/lib/python3.6/site-packages/traitlets/config/application.py", line 87, in catch_config_error
return method(app, *args, **kwargs)
File "/glade/work/ddvento/miniconda3/lib/python3.6/site-packages/notebook/notebookapp.py", line 1602, in initialize
self.init_webapp()
File "/glade/work/ddvento/miniconda3/lib/python3.6/site-packages/jupyterhub/singleuser.py", line 433, in init_webapp
self.init_hub_auth()
File "/glade/work/ddvento/miniconda3/lib/python3.6/site-packages/jupyterhub/singleuser.py", line 428, in init_hub_auth
if not self.hub_auth.oauth_client_id:
File "/glade/work/ddvento/miniconda3/lib/python3.6/site-packages/traitlets/traitlets.py", line 556, in __get__
return self.get(obj, cls)
File "/glade/work/ddvento/miniconda3/lib/python3.6/site-packages/traitlets/traitlets.py", line 535, in get
value = self._validate(obj, dynamic_default())
File "/glade/work/ddvento/miniconda3/lib/python3.6/site-packages/traitlets/traitlets.py", line 593, in _validate
value = self._cross_validate(obj, value)
File "/glade/work/ddvento/miniconda3/lib/python3.6/site-packages/traitlets/traitlets.py", line 599, in _cross_validate
value = obj._trait_validators[self.name](obj, proposal)
File "/glade/work/ddvento/miniconda3/lib/python3.6/site-packages/traitlets/traitlets.py", line 907, in __call__
return self.func(*args, **kwargs)
File "/glade/work/ddvento/miniconda3/lib/python3.6/site-packages/jupyterhub/services/auth.py", line 484, in _ensure_not_empty
raise ValueError("%s cannot be empty." % proposal.trait.name)
ValueError: oauth_client_id cannot be empty.
```

All google knows about that error is either:

* do not run `jupyterhub-singleuser` run `jupyterhub` instead (doh!) which of course is not the case in this context
* make sure the jupyterhub version of the two systems connecting to each other is the same (which it is in my case, both are running `v0.9.0`)

Any ideas on what may be wrong here?