Can't say I fully understand what's going on, but it seems gpg-before-2
has some trouble with its agent, at least when using
gnome-session (which stopped using gnome-keyring as a gpg-agent since
Fedora 23 at least).
Sanity seems to be restored when preferring gpg2 instead. "gpg" is used
when gpg2 isn't there; and there's the MU_GPG_PATH env variable to
override all of that.