I am running Proguard via the Maven Plugin, you can see my configuration here: <https://github.com/sanity/tahrir/blob/proguard-debug/pom.xml#L61>

You can see the complete output of "mvn -DskipTests assembly:assembly" here: <https://gist.github.com/ee1081179496e11916cb>

Despite quite a bit of searching I cannot find any explanation of what causes this error, nor now I can fix it?