:pep: directive generates redirected links

[arekfu]

Describe the bug

The :pep: directive generates links to https://www.python.org/dev/peps/pep-$PEP, but the linkcheck builder warns that these URLs are now redirected to https://peps.python.org/pep-$PEP/.

How to Reproduce

$ python3 -m venv ./venv
$ source ./venv/bin/activate
$ pip install sphinx
$ git clone git@github.com:arekfu/sphinx-issue-pep.git && cd sphinx-issue-pep
$ sphinx-build -b linkcheck . _build
Running Sphinx v4.4.0
building [mo]: targets for 0 po files that are out of date
building [linkcheck]: targets for 1 source files that are out of date
updating environment: [new config] 1 added, 0 changed, 0 removed
reading sources... [100%] index
looking for now-outdated files... none found
pickling environment... done
checking consistency... done
preparing documents... done
writing output... [100%] index

(           index: line    4) redirect  https://www.python.org/dev/peps/pep-0008 - permanently to https://peps.python.org/pep-0008/
build succeeded.

Look for any errors in the above output or in _build/output.txt

Expected behavior

No linkcheck warning should be produced.

Your project

https://github.com/arekfu/sphinx-issue-pep

Screenshots

No response

OS

Linux Ubuntu 20.04

Python version

3.8.10

Sphinx version

4.4.0

Sphinx extensions

No response

Extra tools

No response

Additional context

No response

[arekfu]

I just realised this is probably a docutils bug, isn't it?

[arekfu]

Link to the docutils bug report: here

[nijel]

The default value for this is hardcoded in Sphinx as well, #10267 should address this.