Switch back to Maven 3.6.1 due to mojohaus/build-helper-maven-plugin#81

.travis.yml

@@ -26,6 +26,13 @@ jdk:
 # Make sure travis can use container-based infrastructure
 sudo: false
 
+# Switch back to Maven 3.6.1 due to https://github.com/mojohaus/build-helper-maven-plugin/issues/81
+before_install:
+- wget https://archive.apache.org/dist/maven/maven-3/3.6.1/binaries/apache-maven-3.6.1-bin.zip
+- unzip -qq apache-maven-3.6.1-bin.zip
+- export M2_HOME=$PWD/apache-maven-3.6.1
+- export PATH=$M2_HOME/bin:$PATH
+
 install: "mvn -s ./.travis.maven-settings.xml clean"
 
 script: