Since ros/catkin#1048 catkin prefers to use setuptools instead of distutils. The package.xml must include <buildexport_depend> tags for python-setuptools because in ROS Melodic catkin doesn't export that build dependency. I also included a <buildtool_depend> for python3-setuptools, which while catkin does export it, it makes it clear looking at this package.xml in isolation that setuptools is required in both cases.
Since ros/catkin#1048 catkin prefers to use
setuptoolsinstead ofdistutils. Thepackage.xmlmust include<buildexport_depend>tags forpython-setuptoolsbecause in ROS Melodic catkin doesn't export that build dependency. I also included a<buildtool_depend>forpython3-setuptools, which while catkin does export it, it makes it clear looking at thispackage.xmlin isolation thatsetuptoolsis required in both cases.