gym环境错误：gym.error.UnregisteredEnv: No registered env with id: BipedalWalker-v2

gym环境错误：gym.error.UnregisteredEnv: No registered env with id: BipedalWalker-v2

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "TD3_BipedalWalker-v2.py", line 54, in 
    env = gym.make(args.env_name)
  File "/home/B318_ssh/.local/lib/python3.6/site-packages/gym/envs/registration.py", line 75, in make
    spec = self.spec(id)
  File "/home/B318_ssh/.local/lib/python3.6/site-packages/gym/envs/registration.py", line 89, in spec
    raise error.UnregisteredEnv('No registered env with id: {}'.format(id))
gym.error.UnregisteredEnv: No registered env with id: BipedalWalker-v2

因为gym的版本的问题，安装上最新的gym，使用它推荐的“BipedalWalker-v3”就可以了。