Allow current working directory for nbgrader config file only

[brichet]

This PR is to (re)allow loading configuration file from current working directory.
This feature has been removed from jupyter_core for security reasons (GHSA-pq7m-3gw7-gq5x).

This will fix the tests on extensions which are broken since the last release of jupyter_core.

For what I understand it should only load configuration file for nbgrader, it should not reintroduce the security error.

[github-actions]

👈 Launch a Binder on branch brichet/nbgrader/fix/config_dir

[jtpio]

Thanks @brichet 👍

I think that makes sense if a specific file is explicitly loaded and not any in cwd like it was the case before.

Looks like the jupyter_core advisory has now been published: GHSA-m678-f26j-3hrp

[brichet]

Thanks for sharing the correct link.