!!! Multiple package instances within a single package slot have been pulled
!!! into the dependency graph, resulting in a slot conflict:

sys-libs/zlib:0

  (sys-libs/zlib-1.2.3-r1::gentoo, installed) pulled in by
    (no parents that aren't satisfied by other packages in this slot)

  (sys-libs/zlib-1.2.5-r2::gentoo, ebuild scheduled for merge) pulled in by
    >=sys-libs/zlib-1.2.3.1 required by (net-libs/gnutls-2.10.5::gentoo, ebuild scheduled for merge)