Add support for datetime.UTC mandatory for Python > 3.12

git-svn-id: https://redmine.imt-atlantique.fr/svn/xaal/code/Python/branches/0.7@3218 b32b6428-25c9-4566-ad07-03861ab6144f

libs/lib/xaal/lib/messages.py

@@ -323,8 +323,8 @@ def build_nonce(data):
 
 def build_timestamp():
     """Return array [seconds since epoch, microseconds since last seconds] Time = UTC+0000"""
-    epoch = datetime.datetime.utcfromtimestamp(0)
-    timestamp = datetime.datetime.utcnow() - epoch
+    epoch = datetime.datetime.fromtimestamp(0, datetime.UTC)
+    timestamp = datetime.datetime.now(datetime.UTC) - epoch
     return _packtimestamp(timestamp.total_seconds(), timestamp.microseconds)