fix(test): Fix UTC import in test to support python 3.10

Author: abhinand-c

tests/asynchronous/document/test_instance.py

@@ -3,7 +3,14 @@
 import pickle
 import uuid
 import weakref
-from datetime import datetime, UTC
+from datetime import datetime
+try:
+    # Python 3.11+
+    from datetime import UTC
+except ImportError:
+    # Python ≤ 3.10
+    from datetime import timezone
+    UTC = timezone.utc
 from unittest.mock import AsyncMock
 
 import bson

tests/asynchronous/document/test_timeseries_collection.py

@@ -1,6 +1,14 @@
 import asyncio
 import unittest
-from datetime import datetime, timedelta, UTC
+from datetime import datetime, timedelta
+
+try:
+    # Python 3.11+
+    from datetime import UTC
+except ImportError:
+    # Python ≤ 3.10
+    from datetime import timezone
+    UTC = timezone.utc
 
 from mongoengine import (
     DateTimeField,

tests/fixtures.py

@@ -1,5 +1,13 @@
 import pickle
-from datetime import datetime, UTC
+from datetime import datetime
+
+try:
+    # Python 3.11+
+    from datetime import UTC
+except ImportError:
+    # Python ≤ 3.10
+    from datetime import timezone
+    UTC = timezone.utc
 
 from mongoengine import *
 from mongoengine import signals