While working on this for the 1st time. My maven does not like the style of some files and I would get 'There are 2 checkstyle errors' and build failed.
My workaround is to use 'mvn xxx -Dcheckstyle.skip'. However I think it is still nice to fix it in case someone else is also facing this.
$ mvn -v
Apache Maven 3.3.9
OS name: "mac os x", version: "10.11.1", arch: "x86_64", family: "mac"