message: Log errors when the flusher thread fails to flush
diff: @@ -433,7 +433,8 @@ impl Connection<Authenticated> {
  let mut w = wbuf.lock().unwrap();
  w.in_flush = false;
  if cur_len > 0 {
  - if let Err(_) = w.writer.flush() {
  + if let Err(error) = w.writer.flush() {
  + eprintln!("Flusher thread failed to flush: {:?}", error);
  break;
  }
  }
  