`SyntaxError` when byte-compiling during `do-release-upgrade` to hirsute

[Dan Watkins]

When performing a `do-release-upgrade -d` on my groovy system, I saw:

Setting up python3-software-properties (0.99.8) ...
Failed to byte-compile /usr/lib/python3/dist-packages/softwareproperties/extendedsourceslist.py: File "/usr/lib/python3/dist-packages/softwareproperties/extendedsourceslist.py", line 436
    def __init__(self, sourceslist=None, /, files=None):
                                         ^
SyntaxError: invalid syntax (expected ')')

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Marcel Waldvogel (marcel.waldvogel)]

For me, this happened when installing `pypy3` on hirsute.

running pypy3 rtupdate hooks for 7.3
Failed to byte-compile /usr/lib/python3/dist-packages/softwareproperties/extendedsourceslist.py: File "/
usr/lib/python3/dist-packages/softwareproperties/extendedsourceslist.py", line 436
    def __init__(self, sourceslist=None, /, files=None):
                                         ^
SyntaxError: invalid syntax (expected ')')

The problem seems to be that `python3-software-properties` expects Python>=3.8 (the `/` syntax only became available then, see https://www.python.org/dev/peps/pep-0570/). However, pypy3 as packaged with hirsute (7.3.5) only supports Python 3.7. Upgrading to pypy 7.3.6 (https://www.pypy.org/posts/2021/10/pypy-v736-release.html), announced as supporting Python 3.8, probably would solve this problem.