I'm having trouble figuring out how to invoke a python unittest (non-rostest) from within Catkin without getting warnings. I'm invoking catkin_add_nosetests(test/package_test.py) from CMakeLists.txt, but even a successful test run with no output still generates summary output at the end:

Ran 1 test in 0.000s

OK

catkin build --catkin-make-args run_tests seems to interpret this output as a warning:

Starting  >>> package                                                                                                                                                             
______________________________
Warnings   << package:make /home/user/catkin_ws/logs/package/build.make.002.log                                                                                          
.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK
cd /home/user/catkin_ws/build/package; catkin build --get-env package | catkin env -si  /usr/bin/make run_tests --jobserver-auth=3,4; cd -

.......................................................................
Finished  <<< package                [ 0.9 seconds ]
...
[build]   Warnings:  1 packages succeeded with warnings.                                                                                                                                

If I use rosunit.unitrun instead of unittest.main from within the test script, then the script itself no longer generates that summary output. However, catkin's own nosetest infrastructure bypasses my __main__ code and forces it to run with the normal unittest runner anyway.

I'm having trouble figuring out how this is supposed to work. Any pointers on what I'm doing wrong? I'm running ROS Noetic on PopOS/Ubuntu 20.04.