heroku/heroku-buildpack-python — pull request #47 by ojno (2012-06-01 20:13:57+00:00)
Title: Option to purge and recreate virtualenv

With the user_env_compile option letting us pass environment into buildpacks, I added a CLEAN_VIRTUALENV option which deletes the cached virtualenv and recreates it afresh. I found this really useful when trying to trim down the size of my slug.