Generates a sequence of objc errors on macOs Big Sur

[ghost]

For some reason, I'm facing this issue when I run main.py in PyCharm, no errors faced in macOs terminal, which is the subject and according to the complains here is due to added security to restrict multithreading in Mac OS High Sierra and above. Therefore one workaround is to disable the fork safety using an environment variable. I'm working on a fix and I will submit a PR when I'm done.

objc[7715]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.
objc[7715]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
objc[7707]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.
objc[7707]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
objc[7699]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.
objc[7699]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
objc[7698]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.
objc[7698]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
objc[7700]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.
objc[7700]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
objc[7711]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.
objc[7711]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
objc[7721]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.
objc[7721]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
objc[7709]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.
objc[7709]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
objc[7718]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.
objc[7718]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
objc[7702]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.
objc[7702]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
objc[7719]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.
objc[7719]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
objc[7697]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.
objc[7697]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
Traceback (most recent call last):
  File "/Users/emadboctor/Desktop/pytorch-a2c-ppo-acktr-gail/main.py", line 256, in <module>
objc[7713]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.
objc[7713]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
    main()
  File "/Users/emadboctor/Desktop/pytorch-a2c-ppo-acktr-gail/main.py", line 36, in main
    envs = make_vec_envs(
  File "/Users/emadboctor/Desktop/pytorch-a2c-ppo-acktr-gail/a2c_ppo_acktr/envs.py", line 96, in make_vec_envs
    envs = SubprocVecEnv(envs)
  File "/usr/local/lib/python3.8/site-packages/stable_baselines3/common/vec_env/subproc_vec_env.py", line 106, in __init__
    observation_space, action_space = self.remotes[0].recv()
  File "/usr/local/Cellar/[email protected]/3.8.7/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/connection.py", line 250, in recv
    buf = self._recv_bytes()
  File "/usr/local/Cellar/[email protected]/3.8.7/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/connection.py", line 414, in _recv_bytes
    buf = self._recv(4)
  File "/usr/local/Cellar/[email protected]/3.8.7/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/connection.py", line 383, in _recv
    raise EOFError
EOFError
objc[7703]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.
objc[7703]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.

Process finished with exit code 1