contrib/systemd/labgrid-coordinator: improve service

Adding `PYTHONUNBUFFERED=1` [1] to the environment forces the stdout and
stderr streams to be unbuffered, so all logs end up in the journal
instantly.

Add a hint where to get a config template from.

Soften the restart criteria by using `on-failure` instead of `on-abort`,
which covers more failure scenarios, see [2].

[1] https://docs.python.org/3/using/cmdline.html#envvar-PYTHONUNBUFFERED
[2] https://www.freedesktop.org/software/systemd/man/systemd.service.html#Restart=

Signed-off-by: Bastian Krause <bst@pengutronix.de>
(cherry picked from commit 1e24d60)

Author: Bastian-Krause

contrib/systemd/labgrid-coordinator.service

@@ -3,9 +3,11 @@ Description=Labgrid Coordinator
 After=network.target
 
 [Service]
+Environment="PYTHONUNBUFFERED=1"
+# labgrid's .crossbar/config-anonymous.yaml serves as an example
 ExecStart=/path/to/labgrid-coordinator/venv/bin/crossbar start --logformat=syslogd --cbdir /var/lib/labgrid-coordinator --config /etc/labgrid/coordinator.yaml
 ExecStop=/usr/bin/labgrid-coordinator stop --cbdir /var/lib/labgrid-coordinator
-Restart=on-abort
+Restart=on-failure
 DynamicUser=yes
 StateDirectory=labgrid-coordinator