x11-libs/gtk+:2 is dead and needs to go away.
Also, please tell me if we can destabilise this package (drop 2018-r1) in order to avoid the stabilisation rabbithole in bug 769317 (consequently also destabilising sci-mathematics/coq). Its only revdep dev-lang/spark is currently PMASKED anyway due to py27.
My first guess it is that it depends on lablgtk 2 or 3. 3 is preferred