I couldn't make it work with python 2.7.16 (spent way too much time on trying), so I do this with the native python 2.7.5 from the system. Not ideal, but much better than nothing.
Submitting as WIP as this is subject to ATLAS CMake dumping
python_env.txt as suggested by @tadej. That's something to discuss with @akraszna. Once that file is in, we have nice IntelliSense functionality with e.g. class definition peeking: