From https://github.com/Unity-Technologies/ml-agents/issues/4194

Repro:
Run e.g. "mlagents-learn config/ppo/WallJump.yaml --run-id=WallJumper --num-envs=2". This is an invalid combination of arguments; either --env should be passed, or --num-envs should be omitted.

{noformat}
Traceback (most recent call last):
File "c:\users\gdev\anaconda3\envs\rl\lib\runpy.py", line 193, in _run_module_as_main
"__main__", mod_spec)
File "c:\users\gdev\anaconda3\envs\rl\lib\runpy.py", line 85, in _run_code
exec(code, run_globals)
File "C:\Users\gdev\anaconda3\envs\rl\Scripts\mlagents-learn.exe\__main__.py", line 7, in <module>
File "c:\users\gdev\anaconda3\envs\rl\lib\site-packages\mlagents\trainers\learn.py", line 322, in main
run_cli(parse_command_line())
File "c:\users\gdev\anaconda3\envs\rl\lib\site-packages\mlagents\trainers\learn.py", line 318, in run_cli
run_training(run_seed, options)
File "c:\users\gdev\anaconda3\envs\rl\lib\site-packages\mlagents\trainers\learn.py", line 163, in run_training
tc.start_learning(env_manager)
File "c:\users\gdev\anaconda3\envs\rl\lib\site-packages\mlagents_envs\timers.py", line 305, in wrapped
return func(*args, **kwargs)
File "c:\users\gdev\anaconda3\envs\rl\lib\site-packages\mlagents\trainers\trainer_controller.py", line 243, in start_learning
raise ex
File "c:\users\gdev\anaconda3\envs\rl\lib\site-packages\mlagents\trainers\trainer_controller.py", line 214, in start_learning
self._reset_env(env_manager)
File "c:\users\gdev\anaconda3\envs\rl\lib\site-packages\mlagents_envs\timers.py", line 305, in wrapped
return func(*args, **kwargs)
File "c:\users\gdev\anaconda3\envs\rl\lib\site-packages\mlagents\trainers\trainer_controller.py", line 150, in _reset_env
env.reset(config=sampled_reset_param)
File "c:\users\gdev\anaconda3\envs\rl\lib\site-packages\mlagents\trainers\env_manager.py", line 67, in reset
self.first_step_infos = self._reset_env(config)
File "c:\users\gdev\anaconda3\envs\rl\lib\site-packages\mlagents\trainers\subprocess_env_manager.py", line 295, in _reset_env
ew.previous_step = EnvironmentStep(ew.recv().payload, ew.worker_id, {}, {})
File "c:\users\gdev\anaconda3\envs\rl\lib\site-packages\mlagents\trainers\subprocess_env_manager.py", line 92, in recv
raise env_exception
mlagents_envs.exception.UnityEnvironmentException: If the environment name is None, the worker-id must be 0 in order to connect with the Editor.
{noformat}

We should either raise an exception earlier, or ignore --num-envs when connecting to the editor.