title: Handle Network error with Retrofit observable
body: <p>When using Observables with Retrofit how do you handle Network failure?</p>
  
  <p>Given this code:</p>
  
  <pre><code>Observable&lt;GetJobResponse&gt; observable = api.getApiService().getMyData();
  observable
      .doOnNext(new Action1&lt;GetJobResponse&gt;() {
          @Override
          public void call(GetJobResponse getJobResponse) {
              //do stuff with my data
          }
      })
      .doOnError(new Action1&lt;Throwable&gt;() {
          @Override
          public void call(Throwable throwable) {
              //do stuff with error message
          }
      });
  </code></pre>
  
  <p>The request just fails without network and onError is not called.  It does not crash, but fails silently. Logs shows Retrofit getting the error:</p>
  
  <pre><code> java.net.UnknownHostException: Unable to resolve host "api-staging.sittercity.com": No address associated with hostname
       at java.net.InetAddress.lookupHostByName(InetAddress.java:424)
       at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
       at java.net.InetAddress.getAllByName(InetAddress.java:214)
       at com.squareup.okhttp.internal.Dns$1.getAllByName(Dns.java:29)
  </code></pre>
  
  <p>Using callbacks this is simply passed to the onFailure(RetrofitError error).  How can I get this surfaced with RxJava?</p>