node 4 seems to be having issues on travis, these issue have not been reproducible elsewhere.

stefanpenner · stefanpenner · commit 010bcd4a0828 · 2017-03-07T10:04:56.000-08:00
diff --git a/.travis.yml b/.travis.yml
@@ -3,6 +3,11 @@ node_js:
   - "7"
   - "6"
   - "4"
+
+matrix:
+  allow_failures:
+    - node_js: "4"
+
 after_success:
   - "./bin/publish_to_s3.js"
 before_install:
