catkin python package not found

edit

I am trying to use a library that uses catkin as its build system, however I do not require the rest of ROS and would prefer to avoid installing it. From catkin's docs it says that it does not depend upon ROS however I cannot find a way to make it work without it. I am on Windows using WSL2 Ubuntu 20.04 and CMake 3.19.

I have built and installed catkin from source and not installed it from pip. I did change the deb names to python3-* instead of just python-*, while installing deps.

My project top level CMake file is:

cmake_minimum_required(VERSION 3.16)
project(uasgroundrisk)
...
find_package(catkin REQUIRED)
...

The find_package call throws the following error:

/usr/bin/cmake -DCMAKE_BUILD_TYPE=Debug -G "CodeBlocks - Unix Makefiles" <proj>
-- Using CATKIN_DEVEL_PREFIX: <proj>/cmake-build-debug/devel
-- Using CMAKE_PREFIX_PATH: 
-- Found PythonInterp: /usr/bin/python (found suitable version "3.8.5", minimum required is "3") 
-- Using PYTHON_EXECUTABLE: /usr/bin/python
-- Using Debian Python package layout
-- Using empy: /usr/lib/python3/dist-packages/em.py
-- Using CATKIN_ENABLE_TESTING: ON
-- Call enable_testing()
-- Using CATKIN_TEST_RESULTS_DIR: <proj>/cmake-build-debug/test_results
-- Forcing gtest/gmock from source, though one was otherwise available.
-- Found gtest sources under '/usr/src/googletest': gtests will be built
-- Found gmock sources under '/usr/src/googletest': gmock will be built
-- Found PythonInterp: /usr/bin/python (found version "3.8.5") 
-- Using Python nosetests: /usr/bin/nosetests3
-- catkin 0.8.9
-- BUILD_SHARED_LIBS is on
Traceback (most recent call last):
  File "<proj>/cmake-build-debug/catkin_generated/generate_cached_setup.py", line 12, in <module>
    from catkin.environment_cache import generate_environment_script
ModuleNotFoundError: No module named 'catkin.environment_cache'

I am using Python 3 at /usr/bin/python with this symlinked to the proper location which is being used.

$ which python
  /usr/bin/python
$ ls -la /usr/bin | grep python
 ...
 lrwxrwxrwx 1 root   root           7 Mar 24 15:21 python -> python3
 ...

Spinning up an interactive python console for this same binary

$ python
 Python 3.8.5 (default, Jan 27 2021, 15:41:15)
 [GCC 9.3.0] on linux
 Type "help", "copyright", "credits" or "license" for more information.
 >>> import catkin_pkg
 >>> print(catkin_pkg.__file__)
 /usr/lib/python3/dist-packages/catkin_pkg/__init__.py
 >>> catkin_pkg.__version__
 '0.4.23'
 >>> import sys
 >>> sys.path
 ['/usr/lib/python38.zip', '/usr/lib/python3.8', '/usr/lib/python3.8/lib-dynload', '/usr/local/lib/python3.8/dist-packages', '/usr/lib/python3/dist-packages']

This shows that catkin_pkg is there and up to date. The python path does search through /usr/lib/python3/dist-packages which is where catkin python package is. However:

  >>> import catkin.environment_cache import generate_environment_script
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  ModuleNotFoundError: No module named 'catkin.environment_cache'

I suspect this is an environment issue, but I am not sure what environment variables catkin is looking for from the CMake side. As I mentioned, I am using it outside of ROS, so have not run sourced the setup.sh files or run rosdep. Do I need to recreate this within my own CMake script?