Hi!

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

The error is:
env PYTHONPATH=/build/reproducible-path/numcodecs-0.17.0+ds/.pybuild/cpython3_3.15_numcodecs/build /build/reproducible-path/numcodecs-0.17.0+ds/.pybuild/cpython3_3.14_numcodecs/build \
     http_proxy='http://127.0.0.1:9/' https_proxy='https://127.0.0.1:9/' \
python3 -m sphinx -N -E -T -b html . /build/reproducible-path/numcodecs-0.17.0+ds/.pybuild/docs/html/
env: ‘/build/reproducible-path/numcodecs-0.17.0+ds/.pybuild/cpython3_3.14_numcodecs/build’: Permission denied

The solution is to fix the pythonpath variable when generating docs, add
-i python3 to the pybuild invocation.

I've applied the fix in the sandbox [2] 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/4784352/
[2]: https://debusine.debian.net/debian/r-python-python3.15/