only xenial for 3.7

Author: juancarlostong

.travis.yml

@@ -4,7 +4,6 @@ python:
   - "3.4"
   - "3.5.5"
   - "3.6"
-  - "3.7"
   - "pypy"
   - "pypy3"
 install: "pip install -r requirements/core.txt;pip install -r requirements/test.txt"
@@ -33,3 +32,6 @@ jobs:
       script:
         - "ci/trigger_fullstack-sdk-compat.sh"
       after_success: skip
+    - stage: 'Test'
+      python: "3.7"
+      env: DIST=xenial