ethail [1] filed a deletion request for aurora-firetray-git [2]: It seems the plugin only works for current versions of firefox, and doesn't work anymore for aurora channel. Also, I'm going to stop mantaining this package
[1] https://aur.archlinux.org//account/ethail/ [2] https://aur.archlinux.org//pkgbase/aurora-firetray-git/
