Reach 100% statement coverage for the following files:

retag_opus/__init__.py
retag_opus/__main__.py
retag_opus/app.py
retag_opus/cli.py
retag_opus/colors.py
retag_opus/constants.py
retag_opus/description_parser.py
retag_opus/exceptions.py
retag_opus/music_tags.py
retag_opus/tags_parser.py
retag_opus/utils.py