In Ubuntu 12.10 apt-add-repository got moved to software-properties-common

See https://bugs.launchpad.net/ubuntu/+source/cloud-init/+bug/1021418 for information.

The changelog for the quantal python-software-properties http://changelogs.ubuntu.com/changelogs/pool/main/s/software-properties/software-properties_0.92.9/changelog - 0.85 and 0.84 is where the magic happened