feat: test middleware; use zoneinfo; fix datetime warnings

aircox_streamer/management/commands/streamer.py

@@ -6,11 +6,11 @@ to:
 - cancels Diffusions that have an archive but could not have been played;
 - run Liquidsoap
 """
+from datetime import timezone
 import time
 
 from argparse import RawTextHelpFormatter
 
-import pytz
 from django.core.management.base import BaseCommand
 from django.utils import timezone as tz
 
@@ -19,7 +19,7 @@ from aircox_streamer.controllers import Monitor, Streamer
 
 
 # force using UTC
-tz.activate(pytz.UTC)
+tz.activate(timezone.UTC)
 
 
 class Command(BaseCommand):