Install Graphviz on Travis.

drupol · drupol · commit 21829da1f4ef · 2019-06-15T08:38:41.000+02:00
diff --git a/.travis.yml b/.travis.yml
@@ -13,6 +13,9 @@ php:
 - 7.2
 - 7.3
 
+before_install:
+- sudo apt-get install -y graphviz
+
 install:
 - composer install
 
