Allow HHVM failures; See https://github.com/facebook/php-graph-sdk/pull/854\#issuecomment-401978940

SammyK · SammyK · commit 5d26f570eeb6 · 2018-07-06T13:19:16.000-04:00
diff --git a/.travis.yml b/.travis.yml
@@ -18,6 +18,8 @@ matrix:
   include:
     - php: hhvm
       dist: trusty
+  allow_failures:
+    - php: hhvm
 
 before_install:
   - travis_retry composer self-update
