As reported, see URL: dev-vcs/hgsubversion/files/invalid_utf8.tar.gz Binary files like tarballs should be distributed via distfiles. CVS (and in the future, git) doesn't handle binary files well.
30 Jan 2014; Ian Delaney <idella4@gentoo.org> +hgsubversion-1.5.1.ebuild, -files/invalid_utf8.tar.gz, -hgsubversion-1.5.ebuild: bump; update deps, remove -1.5 and invalid_utf8.tar.gz from FILESDIR (qa issue)