mutagen uninstallable?
On my Macbook Pro running Sierra, it is not installed.  However if it is, you should be able to remove it with pip remove mutagen, and reinstall it with pip install mutagen. It should automatically download, build and install mutagen.  Also, make sure your python is updated to the latest version (i. e. 2.7.10).  If not, you may want to install Homebrew and upgrade it through that. 

Homebrew can be installed by /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)", and python can be updated with brew update; brew upgrade.

Link to Homebrew's official website