# cat /etc/polkit-1/rules.d/51-org.libvirt.unix.manage.rules
polkit.addRule(function(action, subject) {
        if (action.id == "org.libvirt.unix.manage" &&
            subject.user == "error") {
                return polkit.Result.YES;
                polkit.log("action=" + action);
                polkit.log("subject=" + subject);
        }
});

# rpm -q libvirt-daemon virt-manager
libvirt-daemon-3.7.0-3.fc27.x86_64
virt-manager-1.4.3-2.fc27.noarch