This command might do for other user instead of the first
sudo su -c "echo 'deb http://download.opensuse.org/repositories/home:/nate-devv:/solarus-debian/xUbuntu_16.04/ ./' > /etc/apt/sources.list.d/solarus.list"
sudo su -c "echo 'deb http://download.opensuse.org/repositories/home:/nate-devv:/solarus-debian/xUbuntu_16.04/ ./' > /etc/apt/sources.list.d/solarus.list"