try again travis-ci

.travis.yml

@@ -1,4 +1,5 @@
 language: python
+
 python:
 - 3.6
 - 3.5
@@ -8,17 +9,24 @@ python:
 - nightly
 - pypy
 - pypy3
+
+group: deprecated-2017Q2  # https://blog.travis-ci.com/2017-06-21-trusty-updates-2017-Q2-launch
+
 matrix:
   allow_failures:
   - python: nightly
   - python: 3.7-dev
+
 services:
 - docker
+
 before_install:
 - sudo service docker restart ; sleep 10  # https://github.com/travis-ci/travis-ci/issues/4778
 - docker run -d --publish=28015:28015 rethinkdb
+
 install:
 - pip install . pytest
+
 script:
 - py.test -v tests