Using Arcade, Python3, and Ubuntu, this library is looking for ffmpeg .so files in the wrong location.
~/.local/lib64/python3.7/dist-packages/pyglet_ffmpeg2/linux_x86_64/libavcodec.so.58.*
~/.local/lib/python3.7/dist-packages/pyglet_ffmpeg/linux_x86_64/libavcodec.so.58.*