Especially "Killed" message, which is normal as 'sleep' is signalled with SIGKILL once session is ready.
@@ -1,2 +1,2 @@
read USERNAME
-su -c 'echo $$ >> /tmp/qubes-session-waiter; [ ! -f /tmp/qubes-session-env ] && exec sleep 365d' - "$USERNAME"
+su -c 'echo $$ >> /tmp/qubes-session-waiter; [ ! -f /tmp/qubes-session-env ] && exec sleep 365d' - "$USERNAME" 2> /dev/null