The Python useflag unnecessarily depends on GTK. I have Copied the ebuild to a local repo, removed the dependency, and then compiled the package without the unwanted GTK3 dependency, besides the GTK UI and setup programs obviously not being present, everything works perfectly fine, in particular ibus-anthy, which requires python. This was done on 1.5.16, but I have strong doubts the GTK dependency is genuine on any other versions. It seems questionable that GTK2 depends on GTK3 as well, but I have not looked at it.
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=5e5033e97723ea4c1eed676d8b62f6fb73a96b90 commit 5e5033e97723ea4c1eed676d8b62f6fb73a96b90 Author: Akinori Hattori <hattya@gentoo.org> AuthorDate: 2018-08-04 13:36:33 +0000 Commit: Akinori Hattori <hattya@gentoo.org> CommitDate: 2018-08-04 13:57:30 +0000 app-i18n/ibus: allow USE="python -gtk" Closes: https://bugs.gentoo.org/662582 Package-Manager: Portage-2.3.40, Repoman-2.3.9 app-i18n/ibus/ibus-1.5.12.ebuild | 3 +-- app-i18n/ibus/ibus-1.5.16.ebuild | 1 - app-i18n/ibus/ibus-1.5.17.ebuild | 1 - app-i18n/ibus/ibus-1.5.18.ebuild | 1 - 4 files changed, 1 insertion(+), 5 deletions(-)