@oprypin I intend to revert #2497 and merge this in 2 days

Unless we want to disable the search plugin for missing locales with a WARNING log instead of crashing like mad?

mkdocs-material does crash if you select a language it does not support

  File "/home/alexys/venv/ultrabug.fr/lib/python3.9/site-packages/material/partials/language.html", line 4, in top-level template code
    {% import "partials/languages/" ~ config.theme.language ~ ".html" as lang %}
  File "/home/alexys/venv/ultrabug.fr/lib/python3.9/site-packages/jinja2/loaders.py", line 197, in get_source
    raise TemplateNotFound(template)
jinja2.exceptions.TemplateNotFound: partials/languages/pp.html

With latest commit, the search plugin will only WARN on unsupported lang configuration:

WARNING  -  Ignoring search.lang "ezn" as it is not a supported language code.
WARNING  -  Ignoring search.lang "coco" as it is not a supported language code.

Removing the offending locales from the search.lang config is fine since this config option allows to be empty and falls back to english anyway.

I've made the tox CI to WARN as well but not fail the CI when a lunr locale is missing.

If you're okay with this, I'll update the tests accordingly

Moved to #2602