autopkgtest mailman3-nose2 failing on ppc64el

[Olivier Gayot]

On ppc64el, the autopkgtest for mailman3 fails consistently (e.g.: https://autopkgtest.ubuntu.com/results/autopkgtest-lunar/lunar/ppc64el/m/mailman3/20230207_121051_39641@/log.gz) with the following exception (only an excerpt):

Traceback (most recent call last):
  File "/tmp/autopkgtest.1f8GwL/build.r9y/src/src/mailman/model/template.py", line 114, in get
    contents = protocols.get(actual_uri, **auth)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/tmp/autopkgtest.1f8GwL/build.r9y/src/src/mailman/utilities/protocols.py", line 40, in get
    response.raise_for_status()
  File "/usr/lib/python3/dist-packages/requests/models.py", line 1021, in raise_for_status
    raise HTTPError(http_error_msg, response=self)
requests.exceptions.HTTPError: 404 Client Error: Not Found for url: http://localhost:8180/missing.txt

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3.11/logging/__init__.py", line 449, in format
    return self._format(record)
           ^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/logging/__init__.py", line 445, in _format
    return self._fmt % values
           ~~~~~~~~~~^~~~~~~~
KeyError: 't'
[...]

I am able to reproduce the failure consistently, by running the following command on a m1.large ppc64el VM:

$ autopkgtest mailman3 --test-name mailman3-nose2 --apt-pocket=proposed --apt-upgrade --add-apt-source='deb-src http://ports.ubuntu.com/ubuntu-ports lunar main universe restricted multiverse' -- lxd ubuntu-daily:lunar