This is my personal implementation of a YouTube-to-MP3 converter using pytube.
Installing pytube
Install directly from source to get newest version. Recommended as new bugs appear quite frequent in my experience.
$ python -m pip install git+https://github.com/pytube/pytube
Put urls linewise in "urls.txt" and simply run the script.
$ python converter.py
$ ./converter.py
Comments are allowed in "urls.txt". They must start with "#" or "!".