Backup Failed dialog is not userfriendly

[Daniël van Eeden]

When Bug #794576 happens the use gets a "Backup Failed" dialog. The dialog has the text "Failed with an unknown error." The main part of the dialog is the python Traceback info. This is too techincal for many users.

So possibilities to make it more friendly:
- Tell the user that the backup has failed and that he/she should try it again later.
- Tell the user to contact the system administrator
- Hide the full Traceback (click a button to see it).
- Display the real error if possible ("OSError: [Errno 107] Transport endpoint is not connected: '/home/user1/.gvfs'"). This makes it easier to google for the error.
- Tell the user to submit a bug (So that in the next release the unknown error can be turned in a known error with some helpfull information)
- Point to a website/wiki with the most common error info and how to solve them.