use duply as a backend for dup
As a suggestion, having a profile = that would run duply with as it's first args duply already does a very hard and good job about wrapping duplicity in a set of profiles. Moreover duply is packaged and maintained.
Side note: using bash (or something else than posix sh) for backupninja would most probably help. IHMO: working with sh scripting is painful for not so much gain.
(from redmine: created on 2015-10-23)
Edited by Guillaume Subiron