The following keyword changes are necessary to proceed:
#required by gnome-extra/libgsf-1.14.23, required by xfce-extra/tumbler-0.1.25[odf], required by @selected, required by @world (argument)
=dev-libs/glib-2.34.3 ~amd64
при этом в gnome-extra/libgsf/libgsf-1.14.23.ebuild:
RDEPEND=">=dev-libs/glib-2.26:2
а установлен dev-libs/glib-2.32.4-r1