Hi!

While rebuilding the python related packages against the Python 3.15rc2
version we found that python-csb43 fails to build from source:
https://debusine.debian.net/debian/r-python-python3.15/artifact/4856732/

 From the log, the error seems to be:

Running Sphinx v9.1.0
loading translations [en]... done
making output directory... done
WARNING: html_static_path entry '_static' does not exist
building [mo]: targets for 0 po files that are out of date
writing output...
building [html]: targets for 8 source files that are out of date
updating environment: [new config] 8 added, 0 changed, 0 removed
reading sources... [ 12%] converter
reading sources... [ 25%] csb
reading sources... [ 38%] formats
reading sources... [ 50%] homebank
reading sources... [ 62%] index
reading sources... [ 75%] ofx
reading sources... [ 88%] records
reading sources... [100%] utils

WARNING: autodoc: failed to import 'aeb43' from module 'csb43'; the
following exception was raised:
Traceback (most recent call last):
   File
"/usr/lib/python3/dist-packages/sphinx/ext/autodoc/_dynamic/_importer.py",
line 131, in _import_from_module_and_path
     module = _import_module(module_name, try_reload=True)
   File
"/usr/lib/python3/dist-packages/sphinx/ext/autodoc/_dynamic/_importer.py",
line 218, in _import_module
     raise ModuleNotFoundError(msg, name=modname)  # NoQA: TRY301
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ModuleNotFoundError: No module named 'csb43'

In other words, it seems like sphinx is failing to find the csb43
module.

Please note that while we ran into this error during the rebuild against
Python 3.15, that doesn't mean that the root cause for the failure is
necessarily the new Python version.

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.

* Margarita Manterola: " Bug#1149339: python-csb43: FTBFS against python
  3.15rc2 (sphinx fails to find the csb43 module)" (Tue, 29 Sep 2026 16:03:14
  +0200):

It seems to be related to Python 3.15 or the testing environment, a fresh test
passes on salsa CI:

https://salsa.debian.org/tryton-team/python-csb43/-/pipelines/1179726

Hi Mathias,
although it doesn't match other Python 3.15 related issues (most
packages are building their sphinx docs without issues).

In order to build against the test archive, which includes not only
python3.15 but also all the relevant build-dependencies rebuilt against
it, you can add the test repository:

  deb http://deb.debusine.debian.net/debian/r-python-python3.15
sid-python3.15 main

The corresponding signing key can be seen in the first section of
https://deb.debusine.debian.net/debian/r-python-python3.15/

To build from a git repository, you can use something like:
  gbp buildpackage --no-clean-source --git-builder='sbuild
--no-run-lintian --extra-repository="deb 
http://deb.debusine.debian.net/debian/r-python-python3.15 sid-python3.15
main" --extra-repository-key="/path/to/signing-keys.asc"'