Make all tests run on Python 3.6

.travis.yml

@@ -11,7 +11,7 @@ install:
 
 jobs:
   include:
-    - python: 2.7
+    - python: 3.6
       stage: test
       script: tox -e py27
 
@@ -21,7 +21,7 @@ jobs:
 
     - stage: publish
       script: skip
-      python: 2.7
+      python: 3.6
       deploy:
         provider: pypi
         user: flyte