new way

debian/NEWS

-szarp (3.21.05) stable; urgency=medium
-
-  Pythondmn now supports Python 3 scripts ONLY.
-  Existing Python 2 scripts MUST be converted to Python 3.
-
- -- Aleksy Barcz <abarcz@newterm.pl>  Fri, 07 May 2021 16:17:59 +0200

debian/szarp-daemons.config

+#!/bin/sh -e
+
+# Source debconf library.
+. /usr/share/debconf/confmodule
+
+# We use debconf note (not recommended) because NEWS won't be displayed if apt-listchanges is not installed.
+# This should be asked once anyway as debconf remembers which questions have been answered.
+db_input high szarp/pythondmn3 || true
+db_go

debian/szarp-daemons.templates

+Template: szarp/pythondmn3
+Type: note
+_Description: Python 3 pythondmn transition
+ Pythondmn now supports Python 3 scripts ONLY.
+ Existing Python 2 scripts MUST be converted to Python 3.