I get this message when emerge -uDNv1 world: dev-texlive/texlive-metapost:0 (dev-texlive/texlive-metapost-2014:0/0::gentoo, ebuild scheduled for merge) conflicts with <dev-texlive/texlive-metapost-2013 required by (media-sound/lilypond-2.18.2:0/0::gentoo, installed) ^ ^^^^ I think it's a problem with the way that texlive-metapost now has slots. Maybe the lilypond ebuild needs some kind of modification to require whatever slot is available? Reproducible: Always emerge --info see attachment.
Created attachment 409012 [details] emerge --info output
This issue is fixed by unmasking lilypond-2.19.15.
I think this is the same problem as #525712. *** This bug has been marked as a duplicate of bug 525712 ***