The same problem exists on Ubuntu 14.04 LTS (Trusty). In this case, add-apt-repository is in package software-properties-common, which depends on python3-software-properties, which depends (needlessly) on unattended-upgrades.
The same problem exists on Ubuntu 14.04 LTS (Trusty). In this case, add-apt-repository is in package software- properties- common, which depends on python3- software- properties, which depends (needlessly) on unattended- upgrades.