private void write(STATUS status, String msg) {
        byte[] bytes = msg.getBytes(StandardCharsets.UTF_8);
        write(status, bytes);
    }
returns stack trace if there was a container exception or empty string
if there was no stacktrace

@param t
@param metadataList
@return
tika-core/src/main/java/org/apache/tika/pipes/PipesServer.java