GeezerVison

Make `versionchanged:: next`` expand to current (unreleased) version.

When a new CPython release is cut, the release manager will replace all such occurences of "next" with the just-released version. (See the issue for release-tools and devguide PRs.)

This is not a security fix, but an internal feature meant to make backporting easier. Pablo allowed it in 3.10-3.11 though. @ambv, do you want it in 3.9?

Tested on Sphinx 2.4 & 4.5 with a local change (like in GH-127827).
(On Sphinx 5 the build fails for an unrelated reason: #98366.)

Co-authored-by: Adam Turner [email protected]
Co-authored-by: Hugo van Kemenade [email protected]
(cherry picked from commit 7d24ea9)

gh-121277: Raise nice error on next as second argument to deprecated-removed (GH-124623)

(cherry-picked from e349f73)

Updates for 3.9: avoid the new sphinx_gettext

(cherry-picked from 3.10: 8773554)