NotImplementedError with gym 0.17.2

[2000222]

I just run " python mbexp.py -env reacher" with gym 0.17.2, but get the following traceback：
Traceback (most recent call last):
File "mbexp.py", line 64, in
main(args.env, "MPC", args.ctrl_arg, args.override, args.logdir)
File "mbexp.py", line 37, in main
cfg = create_config(env, ctrl_type, ctrl_args, overrides, logdir)
File "/home/ubuntu/data/handful-of-trials-pytorch/config/default.py", line 54, in create_config
cfg_module = cfg_source.CONFIG_MODULE()
File "/home/ubuntu/data/handful-of-trials-pytorch/config/reacher.py", line 99, in init
self.ENV = gym.make(self.ENV_NAME)
File "/home/ubuntu/miniconda3/lib/python3.7/site-packages/gym/envs/registration.py", line 145, in make
return registry.make(id, **kwargs)
File "/home/ubuntu/miniconda3/lib/python3.7/site-packages/gym/envs/registration.py", line 90, in make
env = spec.make(kwargs)
File "/home/ubuntu/miniconda3/lib/python3.7/site-packages/gym/envs/registration.py", line 60, in make
env = cls(_kwargs)
File "/home/ubuntu/data/handful-of-trials-pytorch/env/reacher.py", line 18, in init
mujoco_env.MujocoEnv.init(self, os.path.join(dir_path, 'assets/reacher3d.xml'), 2)
File "/home/ubuntu/miniconda3/lib/python3.7/site-packages/gym/envs/mujoco/mujoco_env.py", line 64, in init
observation, _reward, done, _info = self.step(action)
File "/home/ubuntu/miniconda3/lib/python3.7/site-packages/gym/core.py", line 56, in step
raise NotImplementedError
NotImplementedError

Could anyone give me some solutions？ Thank you.

[jingwu6]

Update: I guess I find the issue. Simply change the version of the gym by the following code:

pip install gym==0.8.2

I met the same issue when I ran this code. Hope someone can help us out.

[mbelalsh]

@jingwu6 Thanks. That worked. I also had to downgrade my mujoco-py version to 0.5.7.