Created attachment 459112 [details] app-misc:ca-certificates-20161102.3.27.2-r2:20170107-130630.log See attached log.
You have an invalid GENTOO_MIRRORS setting.
Shoot, that may explain my previous bug report as well (https://bugs.gentoo.org/show_bug.cgi?id=603280). How should I have detected this? Other than random unexplained errors?
It's fairly common for a package to disappear from upstream mirrors, but it should always still be fetchable from gentoo mirrors (if it was able to be mirrored at all). The fact that it tries a gentoo mirrors & throws a 404, is a very strong indicator that your GENTOO_MIRRORS setting is wrong. I navigated to the base dir of your mirror http://ftp.ucsb.edu/pub/mirrors/linux/gentoo/ and it's a 404, so this server doesn't appear to host gentoo files anymore. But I don't really know of a way to immediately & definitively detected when a GENTOO_MIRRORS server name is bad.