Error encountered when building virtual enviornment when using pre-built enviornment

[johnny-wang16]

To reproduce:

1. docker run -it --env MUJOCO_KEY=URL_TO_YOUR_MUJOCO_KEY \ humancompatibleai/adversarial_policies:latest /bin/bash # change tag if built locally
2. ci/build_venv.sh
3. The following error occurs: seems like something wrong with the dependencies of gym[mujoco]