emerge -Dva gimp

These are the packages that would be merged, in order:

Calculating dependencies... done!

The following keyword changes are necessary to proceed:
 (see "package.accept_keywords" in the portage(5) man page for more details)
# required by gimp (argument)
=media-gfx/gimp-9999 **

NOTE: The --autounmask-keep-masks option will prevent emerge
      from creating package.unmask or ** keyword changes.

Would you like to add these changes to your config files? [Yes/No] No

 * In order to avoid wasting time, backtracking has terminated early
 * due to the above autounmask change(s). The --autounmask-backtrack=y
 * option can be used to force further backtracking, but there is no
 * guarantee that it will produce a solution.

emerge: there are no ebuilds to satisfy ">=media-libs/gegl-0.4.14:0.4[cairo]".
(dependency required by "media-gfx/gimp-9999::media-kit" [ebuild])
(dependency required by "gimp" [argument])