maybe this will allow emoji

build.gradle

@@ -101,6 +101,7 @@ mixin {
 javadoc {
     options.addStringOption('Xwerror', '-quiet') // makes the build fail on travis when there is a javadoc error
     options.linkSource true
+    options.encoding "UTF-8"
     source += sourceSets.api.allJava
     classpath += sourceSets.api.compileClasspath
 }