Add information for the user to update Python version

A descriptive error can not be thrown, as line "from __future__ imports"
must occur at the beginning of the file, but older Python
does not recognize __future__ and throws an error immediately.
Therefore, a comment is used to inform user to update his Python
version.

Signed-off-by: Monika Kairaityte <[email protected]>

podman_compose.py

@@ -7,7 +7,7 @@
 # https://docs.docker.com/compose/django/
 # https://docs.docker.com/compose/wordpress/
 # TODO: podman pod logs --color -n -f pod_testlogs
-from __future__ import annotations
+from __future__ import annotations # If you see an error here, use Python 3.7 or greater
 
 import argparse
 import asyncio.exceptions