Gentoo's Bugzilla –
Attachment 318456 Details for
Bug 427000net-misc/unison-2.27.157 fails during emerge: File "/var/tmp/portage/net-misc/unison-2.27.157/work/unison-2.27.157/uigtk2.ml", line 1, characters 0-1: Error: /usr/lib64/ocaml/lablgtk2/gdk.cmi is not a compiled interface