There are various places, mostly in _termui_impl, that use os.system. Python has recommended using subprocess (call, Popen) instead for quite some time. Replace all occurrences of os.system with subprocess.call or Popen, passing a list of args (not a string command). This will require a bit of care since there's a few places that write command strings that can't be directly translated to args lists, and we should ensure the expected commands continue to work on Windows, Mac, and Linux.