Merge pull request #889 from micw523/docs

Update docs python version for Travis CI

Author: k8s-ci-robot

.travis.yml

@@ -13,7 +13,7 @@ matrix:
        env: TOXENV=py27-functional
      - python: 2.7
        env: TOXENV=update-pycodestyle
-     - python: 2.7
+     - python: 3.7
        env: TOXENV=docs
      - python: 2.7
        env: TOXENV=coverage,codecov