Loosen doc/requirements.txt

[EwoutH]

Loosen the package requirements in doc/requirements.txt.

• docutils<0.18 allows docutils 0.17.1 and maybe a future 0.17.2
• sphinx and sphinx_bootstrap_theme now only have minimal versions

This enables the docs to be build with Python 3.10.

[mwaskom]

Hi, is there a problem you had that motivated this change? The Sphinx and sphinx-bootstrap versions were pinned for a reason, I believe.

[EwoutH]

Thanks for the very quick reply! I'm trying to build the docs with Python 3.10, to revert #2685. To do that, at least sphinx v4.3.0 is needed.

On my branch, the docs build with the loosend requirements passes with both Python 3.9 and 3.10.

[mwaskom]

Yes but, if I remember correctly, they look wrong with more recent sphinxes.

[EwoutH]

I did a test run in which I generated all the docs and uploaded them as artifact. When viewing them in a .rst viewer they look fine.

In #2393 the doc/requirements.txt was updated, pinning sphinx and sphinx_bootstrap_theme at seemingly arbitrary version, and removing the comment that is messed up the css. Might that issue be fixed in later versions?

[mwaskom]

I think you're right that whatever specific issue I had in mind is no longer a problem. But still, that doesn't answer whether is there a reason for this update? Pinning the versions prevents builds from suddenly breaking and causing problems, or from having something upstream cause a change in outputs and missing it at the version when it happened, making it harder to debug.

Also, for some reason, your artifact build is missing plots on the introduction page and for the first three sections of the tutorial.

[mwaskom]

Thanks @EwoutH but I don't think it's the right time to update these versions since there apparently is some issue preventing a full build of the docs. I'd like to move over to the pydata theme anyway (#2093) and don't think it's worth it to spend a lot of time making the current version of the docs work on newer versions of sphinx. I did pull your tweak to the docutils version requirement into #2704 (odd that docutils doesn't use .0 for micro releases; I didn't even realize they did them).