Encode process sometimes hangs

[fluffy-critter]

Describe the bug

Sometimes the builder hangs indefinitely.

Reproduction steps

Intermittent issue.

If running from the CLI, ^C results in:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/Users/fluffy/projects/bandcrash/bandcrash/cli.py", line 164, in main
    for task in concurrent.futures.as_completed(all_tasks):
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/concurrent/futures/_base.py", line 243, in as_completed
    waiter.event.wait(wait_timeout)
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/threading.py", line 629, in wait
    signaled = self._cond.wait(timeout)
               ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/threading.py", line 327, in wait
    waiter.acquire()
KeyboardInterrupt
Exception ignored in: <module 'threading' from '/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/threading.py'>
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/threading.py", line 1560, in _shutdown
    atexit_call()
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/concurrent/futures/thread.py", line 31, in _python_exit
    t.join()
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/threading.py", line 1119, in join
    self._wait_for_tstate_lock()
  File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/threading.py", line 1139, in _wait_for_tstate_lock
    if lock.acquire(block, timeout):
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

However this doesn't really tell me which process is failing to complete. The console log leading up to the hang during ./make test is:

Finished writing test_output/album/mp3/13 Test Track.mp3
Zipfile: Waiting for test_output/album/mp3 (1 tasks)
Zipfile: Waiting for test_output/album/ogg (1 tasks)
Cleaning up directory test_output/album/mp3
Allowed in test_output/album/mp3: {'03 .mp3', '02 This has no preview blah blah blah.mp3', '09 .mp3', '12 3. Solave.mp3', '04 Sluggy Puppernutters - A different artist.mp3', '06 asdfasdf.mp3', '11 2. Rinfrescante.mp3', '10 1. Adagio.mp3', '13 Test Track.mp3', '05 Test Track.mp3', '07 This track is hidden.mp3', '08 Test Track with profanity.mp3', '01 This has a title.mp3'}
Removing extraneous file test_output/album/mp3/extraneous-file.txt
Removing extraneous file test_output/album/mp3/dir_should_be_removed
Building test_output/album/Test artist - Test album - mp3.zip from directory test_output/album/mp3
Wrote image bclogo.400.png
added preview protections {'width': 200, 'height': 200, '1x': 'bclogo.200.png', '2x': 'bclogo.400.png'}
Writing index.html
text=<class 'list'>  ['This album was made with Bandcrash.', '', '![](../../art/bclogo.png)']
image alt= url=../../art/bclogo.png title=None
got url ../../art/bclogo.png
added file image-bclogo.png
Writing player.js
Writing player.css
Preview: Finished generating web preview at test_output/album/preview; protections={'2f0a4661f82487ec5024bcef6c055e95.mp3', 'user.css', 'player.css', 'album_cover.200.png', 'album_cover.400.png', 'player.js', 'image-bclogo.png', 'bclogo.400.png', 'index.html', 'bclogo.200.png'}
Cleaning up directory test_output/album/preview
Allowed in test_output/album/preview: {'2f0a4661f82487ec5024bcef6c055e95.mp3', 'user.css', 'player.css', 'album_cover.200.png', 'album_cover.400.png', 'player.js', 'image-bclogo.png', 'bclogo.400.png', 'index.html', 'bclogo.200.png'}
Building test_output/album/Test artist - Test album - preview.zip from directory test_output/album/preview

which doesn't really clear anything up.

Debugging this will probably require adding more logging, and a KeyboardInterrupt handler on the CLI which prints the pending/incomplete tasks before aborting. It's probably something dumb.

Additional context

Mostly happens during development