final MessageQueue errs = new EchoingMessageQueue(
err, mc, false);
RenderContext rc = new RenderContext(
new JsMinimalPrinter(new Concatenator(out, new Callback<IOException>() {
public void handle(IOException ex) {
errs.addMessage(
MessageType.IO_ERROR,
MessagePart.Factory.valueOf(ex.getMessage()));
}
})));