Add proguard rule
@@ -73,6 +73,8 @@ task proguard(type: ProGuardTask, dependsOn: shadowJar) {
dontwarn 'com.google.common.util.**'
dontwarn 'javax.xml.xpath.**'
dontnote '**'
+ // between Java 1.8 and 1.9, the signature of `flip()` changed, which trips up proguard.
+ dontwarn 'org.yaml.snakeyaml.scanner.ScannerImpl'
def outPath = jar.getDestinationDirectory().getAsFile().get().toString()
def extension = jar.archiveExtension.get().toString()
