Use Ubuntu Trusty for Python 3.4 builds

see: travis-ci/travis-ci#9782

Author: Ryan P Kilby

.travis.yml

@@ -10,8 +10,8 @@ matrix:
     include:
       - { python: "2.7", env: DJANGO=1.11 }
 
-      - { python: "3.4", env: DJANGO=1.11 }
-      - { python: "3.4", env: DJANGO=2.0 }
+      - { python: "3.4", env: DJANGO=1.11, dist: trusty}
+      - { python: "3.4", env: DJANGO=2.0, dist: trusty }
 
       - { python: "3.5", env: DJANGO=1.11 }
       - { python: "3.5", env: DJANGO=2.0 }