Hi!

While rebuilding the python related packages against the Python 3.15rc2
version we found that python-pegen fails to build from source [1].

The parser doesn't support Python 3.15. The 3.14 support had been added
as a Debian patch, but the PR was never merged upstream. I have sent a
new upstream PR for the 3.15 support [2].

I've applied this fix in the sandbox [3] to verify that it builds
successfully, please consider applying the patch to support the upcoming
3.15 version.

Setting the severity to important for now. Once Python 3.15 is released,
it will be added to python3-defaults and this bug will become release
critical.

Happy hacking,

[1]: https://debusine.debian.net/debian/r-python-python3.15/artifact/4440301/
[2]: https://github.com/we-like-parsers/pegen/pull/117
[3]: https://debusine.debian.net/debian/r-python-python3.15/