Describe the bug

Python raises a multiprocessing std library UserWarning warning in std error that states something along the lines of:

"...UserWarning: resource_tracker: There appear to be 16 leaked shared_memory objects to clean up at shutdown..."

This is a known issue in Py3.8+ versions of Python multiprocessing and does not appear to be an actual error in downstream shared memory object source.

https://bugs.python.org/issue39959
https://bugs.python.org/issue38119

Possible fix in:

python/cpython#30617

To Reproduce
Install the crunch dependencies and executable on macOS, run the crunch executable with multiple png files simultaneously so that parallel processing is triggered.

Expected behavior
No warning message if this is not an issue that we can address in downstream source.