I put together a quick python script to automate the task of migrating a package from catkin to ament. The script just follows the instructions in the ROS 2 migration guide (note that the script is not yet complete).
You can find the script at: https://github.com/bponsler/ros2-support/blob/master/scripts/catkin-to-ament.py
Additionally a brief explanation of how to use the script here: https://github.com/bponsler/ros2-support/blob/master/tutorials/port-catkin-to-ament.md
As the tutorial says, the script hasn’t been extensively tested and is unlikely to work perfectly but may help reduce the burden of migrating.