Workaround for travis-ci/travis-ci#8552

Atry · Atry · commit d76394bf7c93 · 2017-11-17T17:11:43.000+08:00
diff --git a/.travis.yml b/.travis.yml
@@ -19,6 +19,7 @@ matrix:
       osx_image: xcode8
       language: java
       before_install:
+        - brew update
         - brew install sbt graphviz
 
 before_cache:
