Test / JavaScript build failing on all PRs

[kellietay]

Description

Test / JavaScript is failing in the build on all PRs.

The issue seems to be related to FirefoxHeadless

Reproduce

1. Go to any PR (e.g. Fix unintentional deprecation warnings #3650)
2. Scroll down to see the checks/tests and you can see the failure

Expected Behaviour

This was working previously, for example in #3638

[bollwyvl]

This may be related to ipython/ipykernel#1059. A quick way to see might be to pin to ipykernel !=6.19.*, which i may do in #3653 if it demonstrates the condition described here.

Update: it looks like it's pulling ipykernel-6.16.2 in that failing, so this is apparently not the problem.

[bollwyvl]

The above comment is probably not the case, as we got a couple more releases out, and no improvement.

Along the way, jupyter_server 2.0.2 independently broke some other stuff.

Ideally, moving #3566 forward would be the win, as there's really quite a lot of drift, some of which i explored on some rolled back commits in #3653. Even getting some of the formatters and version bumping tools would help.

[bollwyvl]

Here's the fix:

• 3ac0ab3

and the proof:

• https://github.com/jupyter-widgets/ipywidgets/actions/runs/3752362765/jobs/6374429708#step:6:896

If it helps get #3653 merged, I'm happy to do a separate PR.

[maartenbreddels]

Fixed in #3653
Thanks for the report @kellietay, and thanks for digging into this @bollwyvl

[bollwyvl]

Maybe fixed more in #3673