flyingpig [1] filed a deletion request for ibus-clean [2]: `extra/ibus 1.5.23+3+gaa558de8-2` no longer requires `python2` and `gtk2` as dependencies, so `ibus-clean` and `libibus-clean` are redundant.
[1] https://aur.archlinux.org/account/flyingpig/ [2] https://aur.archlinux.org/pkgbase/ibus-clean/
