apt-get source ubuntu-keyring
cd ubuntu-keyring-*/keyrings

cat >gpg.gen <<GEN
%no-protection
Key-Type: DSA
Key-Length: 1024
Subkey-Type: ELG-E
Subkey-Length: 1024
Name-Real: Rich Remer
Name-Email: rich.remer@example.com
Expire-Date: 0
%pubring my.gpg
%commit
GEN

gpg --batch --gen-key gpg.gen
gpg --import < my.gpg 2>/dev/null
gpg --import < ubuntu-archive-keyring.gpg 2>/dev/null

my=$(gpg my.gpg | grep -A1 ^pub | grep ^\s)
ubuntu=$(gpg ubuntu-archive-keyring.gpg | grep -A1 ^pub | grep ^\s)
keys="$my $ubuntu"

gpg --yes --output=ubuntu-archive-keyring.gpg --export $keys

cd ..    # into ubuntu-keyring source directory

dpkg-buildpackage -rfakeroot -m"Rich Remer <rich.remer@example.com>" -k$key

dpkg-buildpackage: info: source package ubuntu-keyring
dpkg-buildpackage: info: source version 2016.10.27
dpkg-buildpackage: info: source distribution zesty
dpkg-buildpackage: info: host architecture amd64
 dpkg-source --before-build ubuntu-keyring-2016.10.27
 fakeroot debian/rules clean
test -f keyrings/ubuntu-archive-keyring.gpg
rm -f foo foo.asc *.bak *~ */*~ debian/files* debian/*substvars
rm -rf debian/tmp debian/ubuntu-keyring-udeb
 dpkg-source -b ubuntu-keyring-2016.10.27
dpkg-source: warning: no source format specified in debian/source/format, see dpkg-source(1)
dpkg-source: info: using source format '1.0'
dpkg-source: info: building ubuntu-keyring in ubuntu-keyring_2016.10.27.tar.gz
dpkg-source: info: building ubuntu-keyring in ubuntu-keyring_2016.10.27.dsc
 debian/rules build
make: Nothing to be done for 'build'.
 fakeroot debian/rules binary
test -f keyrings/ubuntu-archive-keyring.gpg
test root = "`whoami`"
gpg --no-default-keyring --keyring /usr/share/keyrings/debian-keyring.gpg --decrypt SHA512SUMS.txt.asc | sha512sum -c -
keyrings/ubuntu-archive-keyring.gpg: FAILED
gpg: Signature made Thu 27 Oct 2016 07:31:05 AM PDT
gpg:                using RSA key CAC2D8B9CD2CA5F9
keyrings/ubuntu-archive-removed-keys.gpg: OK
keyrings/ubuntu-keyring-2012-archive.gpg: OK
keyrings/ubuntu-keyring-2012-cdimage.gpg: OK
keyrings/ubuntu-master-keyring.gpg: OK
gpg: Good signature from "Dimitri John Ledkov <xnox@ubuntu.com>" [unknown]
gpg:                 aka "Dimitri John Ledkov <xnox@debian.org>" [unknown]
gpg:                 aka "Dimitri John Ledkov (Member, Board of Directors) <xnox@spi-inc.org>" [unknown]
gpg:                 aka "Dimitri John Ledkov (2015) <dimitri.ledkov@canonical.com>" [unknown]
gpg: WARNING: This key is not certified with a trusted signature!
gpg:          There is no indication that the signature belongs to the owner.
Primary key fingerprint: D764 F6CC 2AB5 9A38 B114  7D73 887B 6061 8B3C 16AE
     Subkey fingerprint: 773C 99EB D0A1 1172 217A  7C3F CAC2 D8B9 CD2C A5F9
sha512sum: WARNING: 1 computed checksum did NOT match
debian/rules:88: recipe for target 'checkkeyrings' failed
make: *** [checkkeyrings] Error 1
dpkg-buildpackage: error: fakeroot debian/rules binary gave error exit status 2