This is due to the way that gpg is called from apt-key:
--keyring) shift TRUSTEDFILE="$1" FORCED_KEYRING="$1" if [ -r "$TRUSTEDFILE" ] || [ "$2" = 'add' ] || [ "$2" = 'adv' ]; then GPG="$GPG --keyring $TRUSTEDFILE --primary-keyring $TRUSTEDFILE"
This is due to the way that gpg is called from apt-key:
--keyring)
TRUSTEDFILE= "$1"
FORCED_ KEYRING= "$1"
GPG= "$GPG --keyring $TRUSTEDFILE --primary-keyring $TRUSTEDFILE"
shift
if [ -r "$TRUSTEDFILE" ] || [ "$2" = 'add' ] || [ "$2" = 'adv' ]; then