Found on Python 3.6 on a low-resource platform (NI RoboRIO), it seems that this occurs only because the ProcessPoolExecutor is being imported. A proposed fix would only import ProcessPoolExecutor if -j > 1. Stacktrace follows:

 /usr/local/bin/python3 -m compileall -j 1 /home/lvuser/py
^CTraceback (most recent call last):
  File "/usr/local/lib/python3.6/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/local/lib/python3.6/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/usr/local/lib/python3.6/compileall.py", line 20, in <module>
    from concurrent.futures import ProcessPoolExecutor
  File "/usr/local/lib/python3.6/concurrent/futures/__init__.py", line 17, in <module>
    from concurrent.futures.process import ProcessPoolExecutor
  File "/usr/local/lib/python3.6/concurrent/futures/process.py", line 53, in <module>
    import multiprocessing
  File "/usr/local/lib/python3.6/multiprocessing/__init__.py", line 16, in <module>
    from . import context
  File "/usr/local/lib/python3.6/multiprocessing/context.py", line 5, in <module>
    from . import process
  File "/usr/local/lib/python3.6/multiprocessing/process.py", line 311, in <module>
    _current_process = _MainProcess()
  File "/usr/local/lib/python3.6/multiprocessing/process.py", line 298, in __init__
    self._config = {'authkey': AuthenticationString(os.urandom(32)),