Hi!

While rebuilding the python related packages against the Python 3.15rc1
version we found that python-installer fails to build from source [1].

The problem can be fixed applying upstream's commit 97609d8: Use
os.path.commonpath over commonprefix (#345) [2].

I applied the upstream fix in the sandbox [3] to be able to build the
packages that depend on python-installer, please consider applying the
patch to support the upcoming 3.15 version.

Happy hacking,

[1]: https://debusine.debian.net/debian/r-python-python3.15/artifact/4431389/
[2]: https://github.com/pypa/installer/commit/97609d8b7c202f3a8e5174747559e83c61a4cc95
[3]: https://debusine.debian.net/debian/r-python-python3.15/