Bug#976848: ros-ros-comm needs source upload for Python 3.9 transition

[Adrian Bunk]

Source: ros-ros-comm
Version: 1.15.9+ds1-1
Severity: serious
Control: affects -1 python3-rosgraph python3-roslaunch python3-rosmaster python3-rosmsg python3-rosnode python3-rosparam python3-rospy python3-rosservice python3-rostest python3-rostopic python3-roswtf

Since binNMUs are not possible for binary-all packages,
a source upload is needed for the Python 3.9 transition.

In a more general note, do the tools have to use
the versioned interpreter instead of python3?