Comment 39 for bug 1307545

The last test of the previous comment seems to imply, that we get the unwanted suspending only, if light-locker locks the screen *while* the lid is closed. Heres a test to verify this and takes xfpm out of the whole mess (on utopic):
- killall xfce4-power-manager
- systemd-inhibit --what=handle-lid-switch --who=me --why=test --mode=block sleep 1000
This blocks any action logind may take upon lid close (for 1000 sec.), i.e. one can close the lid and nothing happens.
- sleep 20 && light-locker-command -l
- close the lid

Result: 20 sec. happens nothing (you can even open/close the lid several times). If the lid is closed when "light-locker-command -l" runs, the system suspends.

I would guess, that light-locker lifts the block of the 'handle-lid-switch' and, if the lid is closed, theres still a lid close event pending, which than gets executed (or something of the kind).