fix roll file test at day boundary

iceprod/server/server.py

@@ -7,7 +7,7 @@
 
 import asyncio
 from concurrent.futures import ThreadPoolExecutor
-from datetime import datetime, timedelta
+from datetime import datetime, timedelta, UTC
 import logging
 import os
 import sys
@@ -59,7 +59,7 @@ async def run(self):
 
 
 def roll_files(fd, filename, num_files=5):
-    d = datetime.utcnow()
+    d = datetime.now(UTC)
     ext = (d-timedelta(days=num_files-1)).strftime('%Y-%m-%d')
     newfile = f'{filename}.{ext}'
     if os.path.exists(newfile):  # delete last file

tests/server/server_test.py

@@ -17,7 +17,7 @@
 import shutil
 import subprocess
 import importlib
-from datetime import datetime
+from datetime import datetime, UTC
 import glob
 
 from unittest.mock import AsyncMock, MagicMock
@@ -70,8 +70,7 @@ def test_90_roll_files(tmp_path):
     fd = roll_files(fd, filename)
     assert os.path.exists(filename)
 
-    ext = datetime.utcnow().strftime('%Y-%m')
-    files = glob.glob(f'{filename}.{ext}*')
+    files = glob.glob(f'{filename}.*')
     assert len(files) == 1
 
     fd.write(b'bar')