backup_duplicity_ppa?

Hi,

It seems that installing duplicity on Ubuntu for a PPA using backup_duplicity_ppa has been dropped since version 3.4.1 ( https://github.com/Stouts/Stouts.backup/blob/3.4.1/tasks/install.deb.yml#L5 ). So I am wondering if this a mistake? or if moving forward I should install the PPA first before using this role.

Thank your for your help    
