duplicity /home/USERNAME/MEGAsync/ mega://USERNAME:PASSWORD@mega.co.nz/MEGAsync

sudo pip install mega.py
Requirement already satisfied (use --upgrade to upgrade): mega.py in /usr/local/lib/python2.7/dist-packages
Requirement already satisfied (use --upgrade to upgrade): pycrypto in /usr/lib/python2.7/dist-packages (from mega.py)
Requirement already satisfied (use --upgrade to upgrade): requests in /usr/lib/python2.7/dist-packages (from mega.py)
Cleaning up...

[Login]
Username = myuser@mydomain.com
Password = the-relative-password

duplicity my_local_dir mega://myuser@mega.nz/MEGA_REMOTE_DIR