title: RxJava doOnError vs onError
body: <p>I am try to use the following code</p>
  <pre><code>initLocalSettingsIfNeed()
                              .andThen(initGlobalSettingsIfNeed(configuration))
                              .doOnComplete(callback::onSuccess)
                              .doOnError(throwable -&gt; callback.onError(throwable.getLocalizedMessage()))
                              .subscribe();
  </code></pre>
  <p>But I have exception</p>
  <blockquote>
  <p>The exception was not handled due to missing onError handler in the
  subscribe() method call.</p>
  </blockquote>
  <p>I guess I am not using this methods correctly, I thought can replace <code>doOnComplete</code> <code>doOnError</code> with observer inside <code>subscribe()</code> method, I am wrong?</p>