Bug#891836: systemd: systemctl start/stop/restart valid-template at invalid-instance doesn't cause errors

[Christoph Berg]

Re: To Michael Biebl 2018-03-03 <20180303085701.GA9992 at msg.df7cb.de>
> In that case the error is in a config file, and marking the service as
> faulty makes sense. In the unit at instancetypo case, there's nothing
> wrong with the system.

Fwiw, it looks like AssertPathExists=/etc/postgresql/%I/postgresql.conf
would do what I'm looking for. I'll play with that a bit and report
back.

Christoph