Update to Sphinx 4 and Furo 2021.11, use Python 3.10 in CI

[akx]

This PR:

• unpins Furo to bump it to 2021.11
• updates Sphinx to 4.x (since Furo was holding it back) which is compatible with Python 3.10
• merges in template changes from Furo's base.html and page.html (which had been vendored in and overridden here).
  • I moved the Valohai specific bits into {% include %}able fragments, so merging in future changes should be easier.

With all of this, the diff between master's make html output to this branch's make html output is pretty minimal.

[drazendee]

Hmm.. What am I doing wrong? @akx Pulled the branch, installed new requirements.txt, and then ran the basic make SPHINXOPTS=-E watch but looks like the CSS files didn't load?

It looks like requirements.txt has sphinx-inline-tabs==2021.8.17b10 but that doesn't exist anymore. Can we just unpin this to sphinx-inline-tabs?

[akx]

@DrazenDodik

Hmm.. What am I doing wrong? Pulled the branch, installed new requirements.txt, and then ran the basic make SPHINXOPTS=-E watch but looks like the CSS files didn't load?

Um... works for me.

• nuked virtualenv
• created virtualenv
• git clean -fdx source build
• pip install -r requirements.txt
• make SPHINXOPTS=-E watch
• -> http://127.0.0.1:44044/ shows nicely formatted docs

It looks like requirements.txt has sphinx-inline-tabs==2021.8.17b10 but that doesn't exist anymore. Can we just unpin this to sphinx-inline-tabs?

The version does exist alright. It's marked a prerelease, though... did you get an error trying to install it or..?