Bug 85169

After managing to get my (Debian) system to properly go sleeping using systemd without the pm framework, I ended with a quite ugly solution where I have a service that depends on sleep and stops things at start time and (re-)start them at stop time, so that devices and services that don't like sleep modes are stopped before and restarted after.
If I didn't miss anything, there isn't such a feature yet, so I would suggest to add something like a new "Avoid=" field, which would mean for systemd:
- stop the unit before the avoided unit is started
- note down the stopped unit and all stopped dependencies
- once the avoided unit has been stopped, restart all the avoiding units and what depends on them that was stopped
In this way, a simple "Avoid=sleep.target" added to a service definition would allow for such units sensible to sleep modes to be stopped and re-started properly.
A "Avoid=shutdown.target" could similarly be used to have services not starting automatically to survive a reboot/shutdown cycle if they've been started manually before.