Background backup process hangs on warnings

[Iota]

Some directories I want to backup contain files the user cannot read (which is OK in my case, I only need the readable files). The automatic backup performs anyway, but sends a warning as system notification, and waits for a confirmation.
If I wait too long (seemingly linked to the notification disappearing from screen), clicking on the notification message only tells me a backup is already in progress, therefore I cannot acknowledge any more.
The backup process is still running in the background, doing nothing.
Further backups are *not* performed because of the running one.
This happends almost silently if one misses the first warning.

Killing the backup process solves the issue until the next run.

$ lsb_release -d
Description: Ubuntu 15.10

$ dpkg-query -W deja-dup duplicity
deja-dup 34.0-1ubuntu3
duplicity 0.7.02-1ubuntu1

[Michael Terry (mterry)]

I believe this was fixed by showing an existing progress dialog when Deja Dup is launched...