/etc/apt/source.list

deb http://debian.redlibre.cl/debian/ stretch main contrib non-free
deb-src http://debian.redlibre.cl/debian/ stretch main contrib non-free

deb http://security.debian.org/ stretch/updates main contrib non-free
deb-src http://security.debian.org/ stretch/updates main contrib non-free

deb http://debian.redlibre.cl/debian/ stretch-updates main contrib non-free
deb-src http://debian.redlibre.cl/debian/ stretch-updates main contrib non-free