tests: old python compat

Author: Lancetnik

tests/testcase.py

@@ -1,5 +1,5 @@
 import asyncio
-import datetime
+from datetime import datetime
 from typing import Any
 from unittest.mock import MagicMock
 
@@ -44,7 +44,7 @@ async def handler(msg: str) -> None:
             **{self.subj_name: subject},
             schedule=[
                 {
-                    "time": datetime.datetime.now(datetime.UTC),
+                    "time": datetime.utcnow(),  # old python compat
                 },
             ],
         )