Building GnuPG 2.1.19 in GNU Guix, the test quick-key-manipulation is failing on
our i686 and armhf build machines, like this

Checking quick key generation...
Checking that we can add a user ID...
Checking that we can revoke a user ID...
Checking that we can change the expiration time.
Checking that we can add subkeys...

> () (- - -) (default default never) (rsa sign auth encr seconds=600) (rsa

auth,encr 2) (rsa sign 2105-01-01)
("/tmp/guix-build-gnupg-2.1.19.drv-0/gnupg-2.1.19/g10/gpg"
--no-permission-warning --quick-add-key
"96A345554749A09645AB7EE30510D66843F59F0C" rsa "sign" "2105-01-01") failed:
("gpg: Key generation failed: Invalid value\ngpg: Key not changed so no update
needed.\n")
0: tests.scm:133: (throw (string-append (stringify what) " failed") (:stderr
result))
1: quick-key-manipulation.scm:116: (call-check `(,@gpg --quick-add-key ,fpr ,@args))
2: #<CLOSURE>
3: tests.scm:90: (apply proc args)
4: #<CLOSURE>
5: init.scm:230: (apply proc cars)
FAIL: quick-key-manipulation.scm

full build log from the i686 build machine:
https://hydra.gnu.org/build/1862634/log/raw