app-text/texlive-2016 depends on dev-texlive/texlive-mathscience-2016, which conflicts with dev-texlive/texlive-science. app-doc/pms-6_p20151113 de on the latter, making an update to app-text/texlive-2016 impossible.
commit f5add80db83aba50dd9015184a6564cec0773c58 Author: Alexis Ballier <aballier@gentoo.org> Date: Mon Jan 23 10:02:22 2017 +0100 app-doc/pms: Adjust deps for TeX Live 2016, bug #606790.