Good news. After a few varying attempts I have successfully built 
python3-flit_scm and python3-exceptiongroup using the python build and 
pip install commands.

I have then installed the addon packages on my vm testbed and confirmed 
that the fuse mount command works again with borgbackup.

I will look at using the python build/pip install approach on all the 
python modules for borgbackup as setup.py is flagged as deprecated. If 
that all works then I will submit a patch set for the bug fix.

Learned a lot with this bug issue. Hopefully useful for the future.

Regards,
Adolf.

On 09/05/2023 09:42, Michael Tremer wrote:
> Okay, this sounds like good news.
> 
> I wish there wouldn’t be such massive chaos with every other language’s build system.
> 
> -Michael
> 
>> On 5 May 2023, at 16:34, Adolf Belka <adolf.belka(a)ipfire.org> wrote:
>>
>> Hi Michael,
>>
>> On 04/05/2023 16:51, Michael Tremer wrote:
>>> Hello Adolf,
>>> Another day with another interesting problem that you are bringing us :)
>>
>> I do seem to be able to find things that don't work as expected don't I.
>>> Did you try to run “python3 -m build” in the source directory of exceptiongroup and flit-scm?
>>> That inspiration is coming from here:
>>>    https://github.com/archlinux/svntogit-community/blob/packages/python-exceptiongroup/trunk/PKGBUILD
>>
>> The day before yesterday I thought to myself maybe I should look what Arch Linux does but never followed through on it. Thanks very much for the suggestion. I will give it a go and see how it goes. I will also compare it with the python3-flit module we have because that looks to use the pypproject.toml file, although there are several environment variables defined that I am not sure how to specify for my case but will see how things go.
>>> I am not sure whether we have the build and installer module.
>> We do have build but not installer. The python3-flit module seems to work without using installer, just build so will see how things go to start with only using build before looking at adding installer in as well.
>>
>> Regards,
>> Adolf.
>>
>>> Best,
>>> -Michael
>>>> On 1 May 2023, at 17:52, Adolf Belka <adolf.belka(a)ipfire.org> wrote:
>>>>
>>>> Hi All,
>>>>
>>>> I have figured out why the fuse mount stopped working with borgbackup in Core Update 173. (Bug#13076)
>>>>
>>>>
>>>> python3-trio was updated when python was updated to 3.10.8 and python3-trio is required by python3-pyfuse3. However the python3-trio update also added a new dependency - python3-exceptiongroup which then requires python3-flit_scm for the build of python3-exceptiongroup.
>>>>
>>>>
>>>> Both python3-exceptiongroup and python3-flit_scm use pyproject.toml, however python3-pyproject2setuppy fails with trying to build python3-flit_scm as it does not understand the backend definition in the pyproject.toml file.
>>>>
>>>> The error message is :-
>>>>
>>>>      File "/usr/lib/python3.10/site-packages/pyproject2setuppy/__main__.py", line 50, in main
>>>>      raise NotImplementedError(
>>>>      NotImplementedError: Build backend flit_scm:buildapi unknown
>>>>
>>>>
>>>> pyproject2setuppy is now marked as DEFUNCT due to the number of special cases in the pyproject.toml file that needed lots of work each time to update pyproject2setuppy to work again.
>>>>
>>>>
>>>> Does anyone have any idea how I should build flit_scm and exceptiongroup without using pyproject2setuppy.
>>>>
>>>> I have done some searching but could not find anything that I could either understand or that did not require internet access to download all required dependencies.
>>>>
>>>>
>>>> Regards,
>>>>
>>>> Adolf.
>>>>
>>
>> -- 
>> Sent from my laptop
> 
> 

-- 
Sent from my laptop