title: How to execute producerB if and only if producerA doesn't throw an error?
body: <p>I am trying to work with the below scenario
  I have two producers A and B.
  <code>producerB</code> should execute only when <code>producerA</code> is executed successfully and also if <code>producerA</code> throws error, handle the error and stop there. So I tried something like this.</p>
  
  <pre><code>producerA.flatMapError {
      // handle error and stop right here 
  }.then(producerB).startWithResult { 
      // ...
  }
  </code></pre>
  
  <p>Looks like <code>producerB</code> executes even if <code>producerA</code> throws error.
  Please help me how can I make it work with my scenario.</p>