I'm on the way of simplifying my [pull request for docsbuild-script](https://github.com/python/docsbuild-scripts/pull/1) with two goals in mind:
- Simplify to make it more robust
- Avoid executing external (~untrusted) Makefile on docs.python.org servers
To achieve this, I need to pass sphinx options to the `Doc/Makefile`, I'd like to call, typically:
make autobuild-stable SPHINXOPTS='-D language=fr -D locale_dirs=./locale/'
Which work if `Doc/Makefile` don't erase but append to the `SPHINXOPTS` variable. Which is done by `allow_sphinxopts.diff`.
We may simplify it further by adding `locale_dirs` to `Doc/conf.py` which does not break the english build, but I'm not sure if it's of any interest.
We may abstract it further by accepting a new parameter like SPHINXLANG='fr', with a default of 'en', but in every case I think it's a good thing to allow passing arbitrary SPHINXOPTS so let's start with this?