Github user chemikadze commented on the issue:
https://github.com/apache/incubator-griffin/pull/428
@guoyuepeng as far as I understand, Travis is not preserving state between
builds, and maven artifact caches are anyway not cleaned up at clean phase.
From other hand, looks like [caching](https://docs.travis-ci.com/user/caching/)
can be enabled.---
