# FFMPEG_IMPL=libav emerge -1vp --nodep unpaper
These are the packages that would be merged, in order:
!!! Problem resolving dependencies for app-text/unpaper
!!! The ebuild selected to satisfy "unpaper" has unmet requirements.
- app-text/unpaper-6.1-r1::gentoo-cvs USE="-test" ABI_X86="64" FFMPEG_IMPL="-ffmpeg -libav"
The following REQUIRED_USE flag constraints are unsatisfied:
exactly-one-of ( ffmpeg_impl_ffmpeg ffmpeg_impl_libav )
And user is liek.. wtf? Actually the output should look like:
- app-text/unpaper-6.1-r1::gentoo-cvs USE="-test" ABI_X86="64" FFMPEG_IMPL="-ffmpeg (-libav)"
since USE=libav is p.u.masked on that package. Maybe it should also more verbosely indicate that for REQUIRED_USE, to help users figure out what's happening.