Running `python3 -m pydoc ensurepip` gives me:

https://docs.python.org/3.9/library/ensurepip
but it should be:

https://docs.python.org/3.9/library/ensurepip.html

Issue is in getdocloc function on the line:

    docloc = "%s/%s" % (docloc.rstrip("/"), object.__name__.lower())

But it previously worked as the nginx config for the doc server contains:

    # Emulate Apache's content-negotiation. Was a temporary measure,
    # but now people are using it like a feature.
    location ~ ^/((2|3)(\.[0-8])?|dev)/\w+/[\d\w\.]+(?!\.html)$ {
        if (-f "${request_filename}.html") {
            return 301 https://$host:$request_uri.html;
        }
    }

(So yes "people are using it like a feature" contains pydoc :))

Notice the [0-8], which does not match for my /3.9/.

I propose to fix the issue on both sides:
- On psf-salt to allow 3.9 to get the "temporary" measure.
- pydoc side to simplify the code

This is now fixed on the docs server thanks to [1], so it should work for already release Python 3.9 :)

[1]: https://github.com/python/psf-salt/pull/198

I still did a PR on cpython to avoid a redirection, and get cpython itself out of the "people use this temporary fix as a feature now".

New changeset eb9983c59b0683270328b5c40a115bb028209511 by Julien Palard in branch 'master':
bpo-42869: Avoid an HTTP redirection. (GH-24174)
https://github.com/python/cpython/commit/eb9983c59b0683270328b5c40a115bb028209511