It seem that when python-foo is retired, the script will attempt to remove
python-foo instead of python3-foo (and python3-foo-docs etc.).

Oh. Silly me. I will fix this.

Another idea: The script currently needs fedora-packager (for the pkgname
command). If you use --qf=%{NAME} in the repoquery, it won't.

Yes, I've already created a small PR on those dependencies (another is
using `dnf repoquery` instead of `repoquery` that drops depencendy on
dnf-utils package).

But still I'd rather have this as part of distribution - a package
similar to fedora-obsolete-packages which would allow me to remove all
retired packages simply by installing it.
Oh there is already this proposal -
https://fedoraproject.org/wiki/Changes/Fedora-Retired-Packages

And in the followup discussion this was rejected as a bad idea.

Example: one of the retired packages is "nspr" but if you try to remove it, then half of your system is gone. :)

Therefore it is a good idea to allow user to "cherry-pick" packages which should be kept on machine despite being retired.

Miroslav