I installed on my Jupyter hub server nbgrader. I had problems with nbgrader and so I deinstalled it with
sudo -E conda remove nbgrader
Now I can’t start the Jupyter server for any user. There’s an error
Spawn failed: Server at http://127.0.0.1:33999/user/sylvia/ didn't respond in 30 seconds
What can I do? How can I purge Jupyterhub and reinstall it?