The ebuild is using ${EDITOR} at build time, thus creating an implicit dependency on the ${EDITOR} package. It should use the new gentoo-editor script instead. See tracker bug 294651 for details.
Fixed. + 04 Jul 2010; Thomas Beierlein <tomjbe@gentoo.org> spice-3.5.5-r1.ebuild: + fix for default editor (see bug #294766)