Changes to ros_buildfarm affecting repository import jobs

As we’re getting closer to moving build.ros2.org and build.ros.org to Ubuntu 20.04 we’ve made some changes to reprepro-updater and ros_buildfarm which allow reprepro-updater to run with Python 3. There were some basic smoke checks to confirm the changes wouldn’t harm existing installations but I wanted to announce the changes here in case someone starts having issues they know where to look.

The two patches to reprepro-updater:

If any give you trouble please open issues on the appropriate repository.