Remove global sage.all import in pytest

[tobiasdiez]

📚 Description

Thanks to the recent advantages around sage.all imports (thanks @mkoeppe), we can remove the global sage.all import for pytests. This means that all pytests run now without this global import, and also the collection of tests is way quicker.

Of course, for doctests invoked by pytest the all import is still needed, so it's moved into the corresponding fixture.

📝 Checklist

• The title is concise, informative, and self-explanatory.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation accordingly.

⌛ Dependencies

[mkoeppe]

That would a pleasant surprise if this already works. But where do we see what tests were actually run by pytest? I have the suspicion that it's not running tests, because of the namespace package issue; in https://github.com/sagemath/sage/actions/runs/4863120862/jobs/8670370254?pr=35598, it says

============================= test session starts ==============================
platform linux -- Python 3.8.10, pytest-7.3.1, pluggy-1.0.0
rootdir: /__w/sage/sage/src
configfile: tox.ini
plugins: mock-3.10.0
collected 0 items / 1 skipped

[tobiasdiez]

It was actually an issue with the pytest collection (the skip call for pyx files made it skip all files). This is fixed now. However, there are a few failing tests. Do you have an idea why the import of pyscipopt and cvxpy fail?

[mkoeppe]

They are not standard packages, so not installed

[mkoeppe]

Since these tests never ran, I probably didn't add the magic to conditionalize the tests. Could you help with this?

[tobiasdiez]

Okay, thanks. Was easy enough to fix. So this is ready for review again (the failing doctest seems unrelated).

[github-actions]

Documentation preview for this PR is ready! 🎉
Built with commit: 2085480

[mkoeppe]

Thanks, looking great. I've pushed a small change re the use of a variable from sage.env, which makes it better for downstream.

[tobiasdiez]

Thanks for the review!