Bug#928662: another log flood

[hoxp18]

Dear maintainers,

I found some different type of logs

gnome-shell[PID]: Error checking authorization
   for action id org.freedesktop.packagekit.trigger-offline-update:
   GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed:
   Action org.freedesktop.packagekit.trigger-offline-update
   is not registered

around 20~30 same logs, same PID.

There seems no malfunction at a glance.

Regards.