Unattended/batch key signing

[bedygotr at ruggedinbox.com]

Hello,

I need to do key signing via script.  This command:

/usr/bin/gpg --passphrase-fd 0 --yes --batch --homedir
/path/to/home/.gnupg -u 8B81FA972BF046A1 --edit-key 6C28103815AE3921 sign

Shows me the key being signed and the key being used to sign, and exits
with no errors, exit code 0. If I add --no-tty no output is shown and it
also exits without errors. So I expected it would work, but the keyring
seems unchanged.

Is this impossible? If so, why no errors?

This is with gpg2, which I'd like to stick with if possible.