Fix Pistonball to only render if render_mode is not None

[elliottower]

Description

This fixes a minor bug with Pistonball where the underlying environment code still uses PyGame surfaces and does the mechanism of rendering, even if render_mode is set to none. This causes a problem when trying to train with SB3, as pygame surfaces don't work well with multithreading (pygame.error: Surfaces must not be locked during blit). Also should speed up training in any setting.

Fixes # (issue), Depends on # (pull request)

Type of change

Please delete options that are not relevant.

• 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

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Checklist:

• I have run the pre-commit checks with pre-commit run --all-files (see CONTRIBUTING.md instructions to set it up)
• I have run pytest -v and no errors are present.
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I solved any possible warnings that pytest -v has generated that are related to my code to the best of my knowledge.
• 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

[elliottower]

One problem I found, when calling env.close() on a ProcConcatVec env, I get this error:

Traceback (most recent call last):
  File "/mnt/d/GitHub/SuperSuit/supersuit/vector/multiproc_vec.py", line 65, in async_loop
    instr = pipe.recv()
  File "/home/elliot/anaconda3/envs/pettingzoo/lib/python3.9/multiprocessing/connection.py", line 250, in recv
    buf = self._recv_bytes()
  File "/home/elliot/anaconda3/envs/pettingzoo/lib/python3.9/multiprocessing/connection.py", line 414, in _recv_bytes
    buf = self._recv(4)
  File "/home/elliot/anaconda3/envs/pettingzoo/lib/python3.9/multiprocessing/connection.py", line 379, in _recv
    chunk = read(handle, remaining)
ConnectionResetError: [Errno 104] Connection reset by peer

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/elliot/anaconda3/envs/pettingzoo/lib/python3.9/multiprocessing/process.py", line 315, in _bootstrap
    self.run()
  File "/home/elliot/anaconda3/envs/pettingzoo/lib/python3.9/multiprocessing/process.py", line 108, in run
    self._target(*self._args, **self._kwargs)
  File "/mnt/d/GitHub/SuperSuit/supersuit/vector/multiproc_vec.py", line 114, in async_loop
    pipe.send((e, tb))
  File "/home/elliot/anaconda3/envs/pettingzoo/lib/python3.9/multiprocessing/connection.py", line 206, in send
    self._send_bytes(_ForkingPickler.dumps(obj))
  File "/home/elliot/anaconda3/envs/pettingzoo/lib/python3.9/multiprocessing/connection.py", line 411, in _send_bytes
    self._send(header + buf)
  File "/home/elliot/anaconda3/envs/pettingzoo/lib/python3.9/multiprocessing/connection.py", line 368, in _send
    n = write(self._handle, buf)
BrokenPipeError: [Errno 32] Broken pipe

I tried messing around with pipe.close() and some other multiprocessing things I found on google but it didn't seem to work. If I don't try to call one of these, the program never ends because of the async_loop in multiproc_vec.py. Even if I call sys.exit(0), it still doesn't exit, because of the other threads. This seems like the subject of another PR though.

[elliottower]

One problem I found, when calling env.close() on a ProcConcatVec env, I get this error:

Traceback (most recent call last):
  File "/mnt/d/GitHub/SuperSuit/supersuit/vector/multiproc_vec.py", line 65, in async_loop
    instr = pipe.recv()
  File "/home/elliot/anaconda3/envs/pettingzoo/lib/python3.9/multiprocessing/connection.py", line 250, in recv
    buf = self._recv_bytes()
  File "/home/elliot/anaconda3/envs/pettingzoo/lib/python3.9/multiprocessing/connection.py", line 414, in _recv_bytes
    buf = self._recv(4)
  File "/home/elliot/anaconda3/envs/pettingzoo/lib/python3.9/multiprocessing/connection.py", line 379, in _recv
    chunk = read(handle, remaining)
ConnectionResetError: [Errno 104] Connection reset by peer

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/elliot/anaconda3/envs/pettingzoo/lib/python3.9/multiprocessing/process.py", line 315, in _bootstrap
    self.run()
  File "/home/elliot/anaconda3/envs/pettingzoo/lib/python3.9/multiprocessing/process.py", line 108, in run
    self._target(*self._args, **self._kwargs)
  File "/mnt/d/GitHub/SuperSuit/supersuit/vector/multiproc_vec.py", line 114, in async_loop
    pipe.send((e, tb))
  File "/home/elliot/anaconda3/envs/pettingzoo/lib/python3.9/multiprocessing/connection.py", line 206, in send
    self._send_bytes(_ForkingPickler.dumps(obj))
  File "/home/elliot/anaconda3/envs/pettingzoo/lib/python3.9/multiprocessing/connection.py", line 411, in _send_bytes
    self._send(header + buf)
  File "/home/elliot/anaconda3/envs/pettingzoo/lib/python3.9/multiprocessing/connection.py", line 368, in _send
    n = write(self._handle, buf)
BrokenPipeError: [Errno 32] Broken pipe

I tried messing around with pipe.close() and some other multiprocessing things I found on google but it didn't seem to work. If I don't try to call one of these, the program never ends because of the async_loop in multiproc_vec.py. Even if I call sys.exit(0), it still doesn't exit, because of the other threads. This seems like the subject of another PR though.

This will have to be a separate PR I think, and is more related to SuperSuit and the close() method, so will likely be there instead of here