register tracetools_trace in the ament index
The Python package tracetools_trace
should install an empty marker file to register itself in the ament index. See https://github.com/ament/ament_index/blob/9d42ba13d7694ad8da5b1622e433e691996c4502/ament_index_python/setup.py#L16-L17 for an example.
An upcoming version of colcon-ros
will warn about this file being missing.
After adding this please tag a new release and bloom the package as well as bump the tag in the ros2.repos files.