After the update to roundcube-1.2.0 I enabled the enigma use flag and enabled the plugin. When visiting the GPG settings page, I get an error in roundcube's logfile: [01-Jun-2016 07:47:19 Europe/Berlin] PHP Fatal error: Call to undefined method Crypt_GPG_SubKey::usage() in /var/www/localhost/htdocs/roundcube/plugins/enigma/lib/enigma_driver_gnupg.php on line 437 After digging around in the Crypt_GPG's sources it turns out that the failing method was only introduced in version 1.4.0 of the plugin. I installed dev-php/PEAR-Crypt_GPG-1.4.0 and the enigma plugin started to work. Long story short: the roundcube ebuild should depend on >=dev-php/PEAR-Crypt_GPG-1.4.0 for the enigma plugin.
Note that the Enigma plugin in Roundcube 1.2.0 actually requires >=dev-php/PEAR-Crypt_GPG-1.4.1 which builds as a simple package rename.
commit 079ff90450c6bd739208c3164d0c41d20917ba00 Author: Aaron W. Swenson <titanofold@gentoo.org> Date: Thu Sep 22 14:34:56 2016 -0400 mail-client/roundcube: Version Bump Version bump fixes bug 590608. RDEPEND updated for dev-php/PEAR-Crypt_GPG-1.4.0 fixing bug 584728. Keywords dropped for ~hppa, ~ppc, ~ppc64, and ~sparc due to requirement on >=dev-php/PEAR-Crypt_GPG-1.4.0. (Related bugs: 574264, 594824) Bugs: 584728, 590608 Package-Manager: portage-2.2.28