Thanks for the report! I don't believe the code and/or config for the web server
hosting
docs.python.org is a public repo (may be mistaken), so I'll CC
the director of infrastructure, Ee W. Durbin. I suspect they will know
who to forward this to (or be able to fix it).
Config that’s responsible for redirects lives at
Do we know what the expected behavior is?
3.10 is still in its pre-release cycle, so pages that don't exist in the 3.9 documentation (like the 3.10 What's New doc) need a "dev" or "3.10" in their URL to be reachable.
Only when 3.10 is released and becomes the default version for the Python 3 docs would we expect the OP's link to work.
That said, if nginx config allows for rewrites that only happen when a 404 is about to be emitted otherwise, it would make sense to have "/3/" URLs fall back to "/dev/" URLs before giving up and emitting the 404.
Cheers,
Nick.