with v4.3.0 we will introduce Pamac's ability to build packages. Therefore we changed the way we interact with the AUR. So no extra helper like yaourt is needed anymore. Pamac will fully handle building packages now for it's own.
Guillaume took couple of weeks to accomplish that. Also he managed to get rid of most fo the bugs posted on our github issues list.
Feel free to test this new release within our unstable branch and give us some feedback, before we can call it stable:
sudo pacman -Sy pamac-dev