Following discussion in -dev, I'm updating the book to this one.
Tested:
seahorse gcr gnome-keyring gpgme ImageMagick mercurial xfce4-session
Built, not installed: qca mutt
Problem left: MIT Kerberos cannot be authenticated, because the key is in unsupported pgp2 format.
It is recommended by the developers that befor you backup the directory
~/.gnupg
before upgrading the system to gnupg-2.1.
Two URLs that might help if you have any trouble:
https://wiki.archlinux.org/index.php/GnuPG#Troubleshooting
http://jo-ke.name/wp/?p=111
The latter is cited by the former.