using set -x could produce more debug info.

bestlong · bestlong · commit fc8ffe573163 · 2017-05-25T09:33:40.000+08:00
diff --git a/travis-build.sh b/travis-build.sh
@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 
 #### halt script on error
-set -e
+set -xe
 
 echo '##### Print docker version'
 docker --version
