datetime.UTC symbol not in pythno3.9

Author: d-w-moore

irods/data_object.py

@@ -1,5 +1,5 @@
 import ast
-from datetime import datetime, UTC
+from datetime import datetime, timezone
 import enum
 import io
 import logging
@@ -61,7 +61,7 @@ class _repl_status(enum.Enum):
 
 # An appropriate reference datetime value for gauging replica age as part of
 # the default sort key in PRC4 and onward.
-_REFERENCE_DATETIME = datetime.fromtimestamp(0, UTC)
+_REFERENCE_DATETIME = datetime.fromtimestamp(0, timezone.utc)
 
 
 def REPLICA_NUMBER_SORT_KEY_FN(row):