use xenial

Author: juancarlostong

.travis.yml

@@ -1,4 +1,5 @@
 language: python
+
 python:
   - "2.7"
   - "3.4"
@@ -7,6 +8,10 @@ python:
   - "3.7"
   - "pypy"
   - "pypy3"
+
+env:
+  - SKIP=false
+
 install: "pip install -r requirements/core.txt;pip install -r requirements/test.txt"
 before_script: "pep8"
 addons:
@@ -17,12 +22,14 @@ after_success:
 
 # Integration tests need to run first to reset the PR build status to pending
 stages:
-  - 'Integration tests'
-  - 'Test'
+  - name: 'Trigger Integration tests'
+    if: env(SKIP) = true
+  - name: 'Test'
+    if: env(SKIP) = false
 
 jobs:
   include:
-    - stage: 'Integration tests'
+    - stage: 'Trigger Integration tests'
       env: SDK=python
       language: python
       before_install: skip
@@ -33,3 +40,7 @@ jobs:
       script:
         - "ci/trigger_fullstack-sdk-compat.sh"
       after_success: skip
+
+    - stage: 'Test'
+      if: TRAVIS_PYTHON_VERSION =~ /^3.7/
+      dist: xenial