Alright, so after I set up the environment using pip and virtualenv, I see it has python in it, etc. If I use pip freeze > requirements.txt, it lists the packages I have installed using pip, but it doesn't list anything for the python version itself. How do I make sure the right python version gets captured if I don't check in the /env/ folder?
I think this works well as a convention even if you're not deploying to Heroku. I also like the suggestion to put a guard in setup.py that checks sys.version_info.