Python 3 Travis testing for acme.
Python 3 Travis testing for acme.

Despite its description,
https://github.com/letsencrypt/letsencrypt/pull/630, removed not only
Python 2.6 support, but also Travis tests against Python 3. ACME
library supports Python 3 and Travis should tests it.

This must be merged before any pending PRs agains acme library.

twstrike/le_for_patching,VladimirTyrin/letsencrypt,letsencrypt/letsencrypt,brentdax/letsencrypt,stweil/letsencrypt,DavidGarciaCat/letsencrypt,jsha/letsencrypt,jsha/letsencrypt,stweil/letsencrypt,dietsche/letsencrypt,mitnk/letsencrypt,kuba/letsencrypt,mitnk/letsencrypt,bsmr-misc-forks/letsencrypt,jtl999/certbot,lmcro/letsencrypt,thanatos/lets-encrypt-preview,bsmr-misc-forks/letsencrypt,twstrike/le_for_patching,lmcro/letsencrypt,thanatos/lets-encrypt-preview,dietsche/letsencrypt,wteiken/letsencrypt,letsencrypt/letsencrypt,TheBoegl/letsencrypt,kuba/letsencrypt,wteiken/letsencrypt,brentdax/letsencrypt,VladimirTyrin/letsencrypt,DavidGarciaCat/letsencrypt,jtl999/certbot,TheBoegl/letsencrypt