Raise minimum required version of mujoco to 2.3.6

[traversaro]

Description

mjtState used in #928 was added in mujoco 2.3.6, see google-deepmind/mujoco@f67e359 . I am not sure if it make anyhow sense to permit a lower version of mujoco for users that do not use mujoco.utils.get_state, but anyhow I think a PR with the concrete proposed change is more convenient to discuss then an issue.

Furthermore, I am not familiar with how mujoco_py works and if this additional constraint could be a problem.

Type of change

Please delete options that are not relevant.

• Documentation only change (no code changed)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• I have run the pre-commit checks with pre-commit run --all-files (see CONTRIBUTING.md instructions to set it up)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[Kallinteris-Andreas]

1. Those functions check for mujoco>="2.3.6"

2. The older versions are still supported to maintain exact reproducibility for RL experiments

3. I am assuming your problem is that test_mujoco_v5.test_reset_state fails on the older versions of mujoco, in that case we can simply skip the tests

if mujoco.__version__ < "2.3.6":
    return  # the test relies on `mjtState` which was added on "2.3.6"

[traversaro]

Thanks for the pointers, I missed the assert in the functions and the fact that mujoco env can still run with older versions, as those functions are just called by users (if they want). At this point, the point is that mujoco>=2.1.5 holds as run dependency, while mujoco>=2.3.6 is effectively the test dependency (a bit like pytest is a test dependency but not a run dependency). I can add this on the conda side, thanks!