See the tracker bug. if [[ -n ${REPLACING_VERSIONS} ]] && ! version_is_at_least 1.2.18-r2 ${REPLACING_VERSIONS} ]]; then This will misbehave when REPLACING_VERSIONS has >1 value.
commit db0af7c298f2077a4041387f3e11ae0ed3afb133 Author: Matthias Maier <tamiko@gentoo.org> Date: Wed Jul 27 20:31:49 2016 -0500 app-emulation/libvirt: Do not use REPLACING_VERSIONS, bug #589452 Package-Manager: portage-2.2.28