Fix Travis build

Author: snago

.travis.yml

@@ -36,12 +36,10 @@ matrix:
     env: CUSTOM_MVN_VERION="3.6.0"
   - stage: checkstyle
     jdk: oraclejdk9
-    script: mvn clean verify -Pcheckstyle -Dcheckstyle.version=8.2 -Dmaven.test.skip=true -B
-    env: CHECKSTYLE=8.2
+    script: mvn clean verify -Pcheckstyle -Dmaven.test.skip=true -B
   - stage: checkstyle
     jdk: oraclejdk8
     script: mvn clean verify -Pcheckstyle -Dmaven.test.skip=true -B
-    env: CHECKSTYLE=8.2
   - stage: coveralls
     jdk: oraclejdk8
     env: