How to install mutagen?
mutagen is available in the official Kodi repository which is included by default in Kodi. You can install this addon by going in Kodi to System >> Settings >> Addons >> Get Addons >> XBMC.org Addons or Kodi.tv Addons
About SuperRepo and mutagen
SuperRepo does not maintain mutagen. We only provide an automated index for Kodi users to have easy access to mutagen and other addons for Kodi. We are not affiliated with the developers (Joe Wreschnig) and do not provide help for this particular addon.