ikazuhiro/semi-epg — pull request #1 by dmj (2012-03-04 20:07:55+00:00)
Title: Filter out unusable keys

* mime-edit.el (mime-edit-pgp-key-usable-p): New function. Return
non-nil if key is usable for specified usage.
(mime-edit-pgp-get-signers, mime-edit-encrypt-pgp-mime): Use function.

I had to add this to get SEMI-EPG working with my keyring. The keyring contains some expired key pairs and signing messages failed because SEMI tried to sign with one of the expired keys.