I was attempting to setup a PKA DNS record to allow gpg to find my key through DNS. I
was following instructions found here:

http://www.gushi.org/make-dns-cert/HOWTO.html

I have tested this with 'gpg (GnuPG) 1.4.12' on Ubuntu and it works as expected with
the following command:

echo "foo" | gpg --no-default-keyring --keyring /tmp/gpg-$$ --encrypt --armor --auto-
key-locate pka -r glenn@rempe.us --verbose

gpg: requesting key BECCAE17 from http server www.rempe.us
gpg: pub 4096R/BECCAE17 2014-10-02 Glenn Rempe <glenn@rempe.us>
gpg: using PGP trust model
gpg: NOTE: signature key CF97D091 expired Thu 01 Oct 2015 07:55:20 PM PDT
gpg: key BECCAE17: public key "Glenn Rempe <glenn@rempe.us>" imported
gpg: 1 keys cached (21 signatures)
gpg: 0 keys processed (0 validity counts cleared)
gpg: no ultimately trusted keys found
gpg: Total number processed: 1
gpg: imported: 1 (RSA: 1)
gpg: automatically retrieved `glenn@rempe.us' via PKA
...etc OK...

However, if I try the same command with version 2.1.10 I get the following error
message:

$ echo "foo" | gpg2 --no-default-keyring --keyring /tmp/gpg-$$ --encrypt --armor --
auto-key-locate pka -r glenn@rempe.us
gpg: error retrieving 'glenn@rempe.us' via PKA: Not implemented
gpg: glenn@rempe.us: skipped: Not implemented
gpg: [stdin]: encryption failed: Not implemented

Here is the DNS record. I've left it in place for testing.

$ dig +short glenn._pka.rempe.us. TXT
"v=pka1\;fpr=497A6138963D6C47202B238BA4A288A3BECCAE17\;uri=http://www.rempe.us/download
s/keys/0xA4A288A3BECCAE17.asc"