Fix Python 3.12 compatibility

[frenzymadness]

.joinpath with an empty argument no longer works as before thanks to this change in CPython: python/cpython@cea910e#diff-2e741d925220d74a9cc04cda1314d3649d9d189c0efc7db18e5387a51225b61c

This change mimics the old internal behavior by using _paths attribute directly.

I'm not saying it's perfect but it's the shortest solution I was able to come up with when building notebook 7rc2 with Python 3.12 in Fedora rawhide.

[github-actions]

👈 Launch a Binder on branch frenzymadness/notebook/patch-3

[frenzymadness]

I've reported the issue in CPython upstream: python/cpython#106614

[jtpio]

Thanks @frenzymadness for looking into this.

Looks like the lint failure might be relevant (Python 3.11 is used in the workflow).

[frenzymadness]

I'm not sure what to do here and I'm at EuroPython now so I don't have much time to look into it. The problem is that documentation says that files returns Traversable and it's true that Traversable does not have _path attribute but in this specific case, files returns MultiplexedPath which is a subclass of Traversable and it has that attribute. This is also true in Python 3.11 so it's nothing coming with the new release.

[jtpio]

Since it's just the lint check failing, maybe we can add a comment to ignore the check?

The tests seem to be passing on 3.8 and 3.11.

[jtpio]

Also maybe we could start testing on Python 3.12 on CI too? (and add it to the matrix)

[frenzymadness]

This is not really a big deal so if you are okay with skipping the check, so I am. I dug a little bit deeper and opened one more issue for importlib.resources where a change in typing might fix the problem here: python/importlib_resources#286

[jtpio]

I guess it would be fine yes, also this line is only for the tests.

[frenzymadness]

Rebased and added a comment to ignore the typing issue.

[jtpio]

Should we also try adding 3.12 to the test matrix on CI?

[frenzymadness]

Should we also try adding 3.12 to the test matrix on CI?

Good idea but the configuration is kinda complex so I'm not sure I'm able to do it properly.

[jtpio]

Sure, I'll have a look in a separate PR: #6999

[jtpio]

Thanks!