WorkerEventsTests::test_process_notifications_unsupported sometimes fails

I'm going to retry this job as I don't think the failure is related to the change in the relevant MR, but I noticed this failure in https://salsa.debian.org/AyushGautam/debusine/-/jobs/9449595/viewer#L5843:

___________ WorkerEventsTests.test_process_notifications_unsupported ___________
[gw0] linux -- Python 3.13.5 /usr/bin/python3
self = <debusine.worker.tests.test__worker.WorkerEventsTests testMethod=test_process_notifications_unsupported>
    async def test_process_notifications_unsupported(self) -> None:
        await self.worker.event_queue.put("invalid")  # type: ignore[arg-type]
        with (
            self.assertLogs(level=logging.WARNING) as log,
        ):
            await self.worker.process_notifications()
>       self.assertEqual(
            log.output, ["WARNING:root:Ignoring unsupported event: invalid"]
        )
E       AssertionError: Lists differ: ['WAR[41 chars]alid', "WARNING:asyncio:Executing <Task pendin[426 chars]nds"] != ['WAR[41 chars]alid']
E       
E       First list contains 1 additional elements.
E       First extra element 1:
E       "WARNING:asyncio:Executing <Task pending name='Task-209' coro=<WorkerEventsTests.test_process_notifications_unsupported() running at /usr/lib/python3/dist-packages/debusine/worker/tests/test__worker.py:815> wait_for=<Future pending cb=[Task.task_wakeup()] created at /usr/lib/python3.13/asyncio/base_events.py:459> cb=[_run_until_complete_cb() at /usr/lib/python3.13/asyncio/base_events.py:181] created at /usr/lib/python3.13/asyncio/runners.py:100> took 0.108 seconds"
E       
E       - ['WARNING:root:Ignoring unsupported event: invalid',
E       ?                                                    ^
E       
E       + ['WARNING:root:Ignoring unsupported event: invalid']
E       ?                                                    ^
E       
E       -  "WARNING:asyncio:Executing <Task pending name='Task-209' "
E       -  'coro=<WorkerEventsTests.test_process_notifications_unsupported() running at '
E       -  '/usr/lib/python3/dist-packages/debusine/worker/tests/test__worker.py:815> '
E       -  'wait_for=<Future pending cb=[Task.task_wakeup()] created at '
E       -  '/usr/lib/python3.13/asyncio/base_events.py:459> cb=[_run_until_complete_cb() '
E       -  'at /usr/lib/python3.13/asyncio/base_events.py:181] created at '
E       -  '/usr/lib/python3.13/asyncio/runners.py:100> took 0.108 seconds']
/usr/lib/python3/dist-packages/debusine/worker/tests/test__worker.py:816: AssertionError
----------------------------- Captured stderr call -----------------------------
<Server sockets=(<asyncio.TransportSocket fd=15, family=2, type=1, proto=0, laddr=('127.0.0.1', 41837)>,)> is serving
------------------------------ Captured log call -------------------------------
INFO     asyncio:base_events.py:1653 <Server sockets=(<asyncio.TransportSocket fd=15, family=2, type=1, proto=0, laddr=('127.0.0.1', 41837)>,)> is serving

@enrico, could you have a look at this please, since you added this test?