title: OkHttp response status code in onFailure method
body: <p>when I user the OkHttp Library with a asynchronous way like this:</p>
  
  <pre><code>call.enqueue(new Callback() {
          @Override
          public void onFailure(Call call, IOException e) {
              e.printStackTrace();
          }
  
          @Override
          public void onResponse(Call call, Response response) throws IOException {
  
          }
      });
  </code></pre>
  
  <p>In the <strong>onFailure</strong> method, how I get the response status code to distinguish different errors. For example, Network error or Server error ?</p>