Description:
deja-dup has a missing dependency to python2-gobject2.
python2-gobject2 has a dependency to pygobject2-devel but that is not enough.

Additional info:
* package version(s)
deja-dup-22.1-1
pygobject2-devel-2.28.6-6
python2-gobject2-2.28.6-6

* config and/or log files etc.

Steps to reproduce:
After a default Arch Linux installation with Gnome I installed deja-dup.
Then I created a "buckup" Folder in my home directory.
Then I configured deja-dup with the following configuration:
Backup Location: local folder
Then I configured deja-dup to store the files in the backup folder I created earlier.
Then I configured deja-dup to take the "Documents" Folder to store it.
Then I created two dummy files in the "Documents" Folder.
Then I clicked "backup now" button.
Then I get the message: "Backup Failed - Failed with an unknown error." Message.
Then I closed deja-dup.
Then I installed "python2-gobject2" -> pacman -S python2-gobject2
Then I started deja-dup again and clicked the "backup now" button.
And do not get the error again...