ubuntu-snappy.firstboot fails when oem snap contains config for snaps not preinstalled, built-in

[Simon Eisenmann]

● ubuntu-snappy.firstboot.service - Run snappy firstboot setup
   Loaded: loaded (/lib/systemd/system/ubuntu-snappy.firstboot.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Thu 2015-10-29 15:58:54 UTC; 31s ago
  Process: 799 ExecStart=/usr/bin/snappy firstboot (code=exited, status=1/FAILURE)
 Main PID: 799 (code=exited, status=1/FAILURE)

Oct 29 15:58:54 localhost.localdomain systemd[1]: Starting Run snappy firstboot setup...
Oct 29 15:58:54 localhost.localdomain snappy[799]: configuring an invalid snappy package
Oct 29 15:58:54 localhost.localdomain /usr/bin/snappy[799]: main.go:57: DEBUG: [/usr/bin/snappy firstboot] failed: configuring an invalid snappy package
Oct 29 15:58:54 localhost.localdomain systemd[1]: ubuntu-snappy.firstboot.service: main process exited, code=exited, status=1/FAILURE
Oct 29 15:58:54 localhost.localdomain systemd[1]: Failed to start Run snappy firstboot setup.
Oct 29 15:58:54 localhost.localdomain systemd[1]: Unit ubuntu-snappy.firstboot.service entered failed state.
Oct 29 15:58:54 localhost.localdomain systemd[1]: ubuntu-snappy.firstboot.service failed.

This error should not be fatal for ubuntu-snappy.firstboot.service

Seen in 15.04/stable and edge.