Long story short, ale-py uses a namespace package of gym.envs.atari and namespace packages aren't supported by setuptools editable mode. This is being worked on with native editable support in pip. I don't know the reason for having our test Dockerfile install as editable, but this shouldn't matter.

We also have to use --import-mode=append so it'll pick up the installed package instead of the local gym/ directory. We could also just change directories but this will work for now.