title: Handling response with no body with Retrofit2 and rxJava2
body: <p>I have a WS which returns 200 with no body if successful
  or 420 with json in error body is unsuccessful</p>
  
  <p>Return type is </p>
  
  <pre><code>Observable&lt;Response&lt;Void&gt;&gt;
  </code></pre>
  
  <p>For some reason in case of error with 420 code <code>onNext(Response&lt;Void&gt; value)</code> is called instead of <code>onError(Throwable e)</code> which is being called for any other unsuccessful requests.</p>
  
  <p>Why only in this case onNext instead of onError is called? It is possible to call onError if the request didn't returned 200?</p>