It is tricky that the test expect an ImportError. But if there is an ImportError, then

if MUJOCO_NOT_INSTALLED:
    raise error.DependencyNotInstalled(
        f"{MUJOCO_IMPORT_ERROR}. (HINT: you need to install mujoco)"
    )

will be useless.
I'd like to split the file, and raise error.DependencyNotInstalled in the file. Then also catch DependencyNotInstalled in the tests.

Update: Actually we don't need raise this error during import because make will trigger __init__, current implementation already raise this error in __init__. Just catch DependencyNotInstalled in the test is enough!

What test do you mean? If you can solve a way that mujoco_py works without mujoco and mujoco works without mujoco_py then could you do that

all test import test.env.utils

Oh, could you just add a DeprecatedError to the try except. That is expected to fail for python 3.6

@YouJiacheng could you fix the PR?

I have found a way to fix it: Catch both ImportError and error.DependencyNotInstalled in test.env.utils.
But I also want to remove from gym.envs.mujoco.mujoco_rendering import RenderContextOffscreen, Viewer from __init__.py to simplify the code!

For the catching both errors, see https://stackoverflow.com/questions/6470428/catch-multiple-exceptions-in-one-line-except-block

If it is necessary to remove that, then it will be a necessary breaking change

• Thanks, I know how to catch both error in one line.
• Not really necessary.
• My PC have some problems with pre-commit environment install, I'm trying to fix it! (Finally I run black manually...)

pre-commit/pre-commit#2402
https://superuser.com/questions/1493887/what-is-the-default-registry-value-for-command-processors-autorun