dev-python/numexpr-2.3.1 doesn't build because it cannot download it. http://numexpr.googlecode.com/ says Please be aware that the numexpr project has been migrated to GitHub. This site has been declared unmaintained as of 2014-01-21. Sorry for the inconveniences.
+ 21 Feb 2014; Sébastien Fabbro <bicatali@gentoo.org> metadata.xml, + numexpr-2.3.1.ebuild: + Fixed src uri, added remote-id +