Travis: Enable fast_finish (#4693)

* .travis.tml: Enable fast_finish

https://blog.travis-ci.com/2013-11-27-fast-finishing-builds/

* https://pip.pypa.io/en/latest/development/#adding-a-news-entry

.travis.yml

@@ -3,6 +3,7 @@ sudo: false
 dist: trusty
 
 matrix:
+  fast_finish: true
   include:
     - env: TOXENV=docs
     - env: TOXENV=lint-py2

news/DEADBEEF.trivial

+