Error in py-dub due to cache directory not existing.

[shane-mason]

The User needs to create 'cache' directory . I used the example, renaming the input file of 'output.avi' to 'static.mp4'

  File "/home/wrongdog/FieldStation42/fs42/guide_tk.py", line 19, in __init__
    self.m_widget.load('runtime/static.mp4')
  File "/home/wrongdog/.local/lib/python3.10/site-packages/tkintervideo/player.py", line 50, in load
    self.audio.export(f'{self.cache_directory}/output.wav',format='wav')
  File "/home/wrongdog/.local/lib/python3.10/site-packages/pydub/audio_segment.py", line 867, in export
    out_f, _ = _fd_or_path_or_tempfile(out_f, 'wb+')
  File "/home/wrongdog/.local/lib/python3.10/site-packages/pydub/utils.py", line 60, in _fd_or_path_or_tempfile
    fd = open(fd, mode=mode)
FileNotFoundError: [Errno 2] No such file or directory: 'cache/output.wav'

Once I created the 'cache' directory, it worked. Would be good to handle its own cache.