added debug options to maven command.

Author: HugoMario

.travis.yml

@@ -77,7 +77,7 @@ script:
   # fail if generators contain tab '\t'
   - /bin/bash ./bin/utils/detect_tab_in_java_class.sh
   # run integration tests defined in maven pom.xml
-  - mvn clean install
+  - mvn clean install -X -e
   - mvn -q --batch-mode verify -Psamples
   # Below has been moved to CircleCI
   # docker: build generator image and push to Docker Hub