As reported on gnupg-devel [0], gpg 2.1.0's removal of support for the
export-reset-subkey-passwd feature breaks the use of gpg with monkeysphere
subkey-to-ssh-agent.

It sounds like there is no resistance to fixing this regression, we just need a
patch.

[0] http://lists.gnupg.org/pipermail/gnupg-devel/2014-October/028919.html