sys-fs/aufs-util and sys-kernel/aufs-sources have each other in RDEPEND. Reproducible: Always
aufs-sources lists aufs-util in PDEPEND, not RDEPEND, which means that emerging aufs-sources will pull in aufs-util after the merge.
I tried to emerge aufs-sources for a cross-ROOT and emerge reported a circular dependency until I emerged both with --nodeps in the host and the ROOT.
Why is the PDEPEND there in the first place, except as to "conveniently" install the utils that go with the fs driver? It should simply be removed from aufs-sources.
Drop PDEPEND in favour of elog msg.