Use script instead of after_script

The former propagates the exit code.

.travis.yml

@@ -3,4 +3,6 @@ language: java
 before_install:
  - sudo apt-get update -qq
  - sudo apt-get install -qq python-pip python-virtualenv libevent-dev
-after_script: src/test/resources/run-s3-tests.sh
+script:
+ - mvn test
+ - ./src/test/resources/run-s3-tests.sh