[just for testing] investigate nbmake error in CI

[cchwala]

Currently some CI runs fail with

=================================== FAILURES ===================================
_____ /home/runner/work/poligrain/poligrain/docs/notebooks/Plotting.ipynb ______
NBMAKE INTERNAL ERROR
Exception ignored in: <socket.socket fd=-1, family=AddressFamily.AF_UNIX, type=SocketKind.SOCK_STREAM, proto=0>

See e.g. https://github.com/OpenSenseAction/poligrain/actions/runs/9502701241/job/26288875441?pr=41

As far as I can tell there is no change in our repo that causes this, but I could also not find open issues on this in other repos. Hence, this PR is meant to investigate this problem. If we find that we cannot fix the problem, we might just disable nbmake for the plattforms were it currently fails.

• [ ] closes #xxxx (Replace xxxx with the GitHub issue number)
• [ ] Tests added and passed if fixing a bug or adding a new feature
• [ ] All code checks from pre-commit passed
• [ ] Added an entry in the CHANGELOG.md file

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.00%. Comparing base (61c4063) to head (185bbfe). Report is 18 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #58 +/- ## ========================================== Coverage 100.00% 100.00% ========================================== Files 3 4 +1 Lines 43 253 +210 ========================================== + Hits 43 253 +210 ```

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[cchwala]

it works without problems here... 😐

good: because it is not a general problem bad: because I do not know what causes the problem in #41

[cchwala]

This problem was fixed in #41 via https://github.com/OpenSenseAction/poligrain/pull/41/commits/cc6babfa3f75a9a5f0fe7673cae6eac0f23dfd42