Github user MikeThomsen commented on the issue:
https://github.com/apache/nifi/pull/2843
@peter-gergely-horvath looks like you have a stylecheck failure. Did you
build the maven module(s) you added using `mvn clean install -Pcontrib-check`?
Looks like you have at least a few files that aren't licensed. Depending on
what they are, you'll need to either add the license header or just exclude
them from the RAT plugin's checks.---
