Although gpg-peset-passphrase allows to set the passphrase for OpenPGP keys,
gpg2 (and gpg) don't work with it. Testing the presetting with
gpg-connect-agent works. However gpg runs a GET_PASSPHRASE, followed by a
CLEAR_PASSPHRASE and another GET_PASSPHRASE. It seems that it is not able to
get the right passphrase back and thus asks again.

Is a trailing nul or LF missing?