src/network/systemd-networkd.rules

// Allow systemd-networkd to set timezone, get product UUID,
// and transient hostname
polkit.addRule(function(action, subject) {
    if ((action.id == "org.freedesktop.hostname1.set-hostname" ||
         action.id == "org.freedesktop.hostname1.get-product-uuid" ||
         action.id == "org.freedesktop.timedate1.set-timezone") &&
        subject.user == "systemd-network") {
        return polkit.Result.YES;
    }
});