Comment # 3 on bug 1001693 from Dominique Leuenberger

I see what's going on:

'adwaita-icon-theme' (icons only) is a requirement for installed systems based
on GTK3 (it's the icons referenced by GTK3 directly) - but to shorten build
loops and cycles, this dependency is being ignored by OBS (there is never a
need to have the icon present to build a package)

installation-images-openSUSE of course is a bit special in this respect - and
it would need to BuildRequires: adwaita-icon-theme here to overcome OBS's
special setup