$ grep ^d-i /tmp/out  | grep string | egrep -i '(en|us)'
d-i     debian-installer/country        string  US
d-i     debconf/language        string  en
d-i     cdrom/codename  string  trusty
d-i     debconf/frontend        string
d-i     keyboard-configuration/layoutcode       string  us
d-i     debian-installer/language       string  en