nbgrader formgrader tab gives vague error: "Sorry, the formgrader encountered an error. Please contact the administrator of the formgrader for further assistance.

I’m running nbgrader + JupyterHub with 1 course and 1 instructor (me). The first assignment was due yesterday; I successfully collected and autograded it (on the command line), then went to the formgrader to finish assigning the grades, but when I click the tab (and any of the subtabs) I get the same message:

Sorry, the formgrader encountered an error. Please contact the administrator of the formgrader for further assistance.

I’ve put both the nbgrader and jupyterhub logs on DEBUG to try and suss out the problem but neither seem inclined to give any details. The closest I get is in the jupyterhub logs, which give 304s for the formgrader elements instead of the expected 200s:

[D 2020-01-24 13:39:56.510 SingleUserNotebookApp auth:871] Allowing whitelisted Hub user magsol
[D 2020-01-24 13:39:56.511 SingleUserNotebookApp log:174] 304 GET /user/magsol/formgrader (magsol@::ffff:128.192.241.125) 1.54ms
[D 2020-01-24 13:39:57.849 SingleUserNotebookApp auth:871] Allowing whitelisted Hub user magsol
[D 2020-01-24 13:39:57.849 SingleUserNotebookApp log:174] 304 GET /user/magsol/formgrader/gradebook (magsol@::ffff:128.192.241.125) 1.57ms
[D 2020-01-24 13:39:58.331 SingleUserNotebookApp auth:871] Allowing whitelisted Hub user magsol
[D 2020-01-24 13:39:58.332 SingleUserNotebookApp log:174] 304 GET /user/magsol/formgrader/manage_students (magsol@::ffff:128.192.241.125) 1.17ms
[D 2020-01-24 13:39:58.967 SingleUserNotebookApp auth:871] Allowing whitelisted Hub user magsol
[D 2020-01-24 13:39:58.968 SingleUserNotebookApp log:174] 304 GET /user/magsol/formgrader/manage_assignments (magsol@::ffff:128.192.241.125) 1.56ms

I’ve been beating my head for a couple hours now and haven’t managed to change the response of the formgrader, so I thought I’d ping the experts.

Operating system

Ubuntu 16.04

nbgrader --version

0.6.1

jupyterhub --version (if used with JupyterHub)

1.0.0 (though I get a very, very strange ERROR:asyncio:Task exception was never retrieved when I run this version command)

jupyter notebook --version

6.0.3

Expected behavior

See the formgrader UI on the web.

Actual behavior

Simply getting the error message.

Steps to reproduce the behavior

This was the first time since setting up the environment that I’ve run the formgrader tab. I’ve run (and re-run) all the jupyter extension install commands in the demos, also with the --overwrite flag, and have re-started the jupyterhub instance multiple times; no change in behavior.

[magsol]

Ok, I figured it out, but it doesn’t make any sense.

After staring at these error messages, the only idea I came up with that made any sense was that JupyterHub/nbgrader truly thought they existed under the “one course, many instructors” environment. It’s not at all the case–I’m the only instructor, teaching only one course–but I shrugged anyway and implemented the formgrader as a JupyterHub service in the config.

I followed the instructions here on the nbgrader website to the letter, and voila. Formgrader works.

As for why JupyterHub seems to think it’s in a multi-instructor setting: I’ve no idea. But it works, so…

I’ll close this issue.

[LukasMueller187]

Unfortunately my certificate chain is still rejected. I’m specifying my cert in the config file. This, however, seems like a tornado issue. I ended up using validate_cert=False as a kwarg in the check_for_local_formgrader function.