Hi!

While rebuilding the python related packages against the Python 3.15rc2
version we found that cdlclient fails to build from source:
https://debusine.debian.net/debian/r-python-python3.15/artifact/4856091/

 From the log, the error seems to be:

   Traceback (most recent call last):
     File "/usr/lib/python3/dist-packages/pyproject_hooks/_impl.py", line
399, in _call_hook
       raise BackendUnavailable(
       ...<4 lines>...
       )
   pyproject_hooks._impl.BackendUnavailable: Cannot import
'setuptools.build_meta'

   TIP pass --env-dir and […] for help debugging a failed build
   ERROR Backend 'setuptools.build_meta' is not available.

I suspect that this issue can be solved by adding a build-dependency on
python3-setuptools.

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