While there are Python 2 and Python 3 Debian packages if catkin_pkg they are not side-by-side installable which has been a long standing issue. If you have every tried to use e.g. python3-ros-buildfarm you have noticed that it basically collides with the core ROS Debian packages like ros-<distro>-catkin.
We will finally tackle this issue and have considered a couple of different approaches. Please see the ticket for more details about the requirements, rational, and approaches. Any feedback is highly welcome. Please comment on the ticket directly.
Cheers,
- Dirk