tests: make test_apscheduler invariant to the TZ environment variable

Make `test_apscheduler` invariant to the `TZ` environment variable,
by specifying the timezone when constructing `AsyncIOScheduler`.
For the purposes of the test, the timezone itself should not matter,
so use UTC.

The `TZ` environment may contain values such as `UTC0` or `GMT+12`,
which is valid but not supported by `tzlocal` that is used by
`apscheduler` behind the scenes.

Author: rokm

tests/test_libraries.py

@@ -108,7 +108,10 @@ def tick():
 
 
         async def main():
-            scheduler = AsyncIOScheduler()
+            # Specify the timezone to use, to make the test invariant to TZ environment variable (which might be set
+            # to UCT0 or GMT+12, which is valid but not supported by `tzlocal` that is used by `apscheduler` behind the
+            # scenes.
+            scheduler = AsyncIOScheduler(timezone=datetime.timezone.utc)
             scheduler.add_job(tick, "interval", seconds=1)
             scheduler.start()