With Py 3.9 out, we should add it to the tests at some point. Maybe that can wait, until 3.9.x, x>0 is out, though

Need to check, if all the job thingies work out, as APS doesn't support py3.9 yet and there has been a report that it doesn't work (with PTB).

On a related note: APS seems to be preparing for v4.0, which will break some stuff, but also supports py3.9 and even uses the new ZoneInfo (also backporting to py3.6+), lifting the restriction to use pytz timezones. I already subscribed to releases. I guess updating APS in PTB should be done only when 4.x, x>0 is out and we're doing breaking things anyway …