title: Reject promise in redux-form in fetch catch-block
body: <p>How does one throw a new SumbmissionError in a .catch-block without getting a unhandled rejection?</p>
  
  <h3>This throws a Unhandled Rejection (SubmissionError)</h3>
  
  <pre><code>import { SubmissionError } from 'redux-form';
  
  const submit = (data) =&gt; {
      console.log(data);
  
      const config = {
          method: 'GET'
      };
  
      return fetch('http://www.notAvailable.com/', config)
          .then(response =&gt; {
              console.log(response)
          })
          .catch(err =&gt; {
              throw new SubmissionError({_error: 'Error'});
          });
  }
  
  export default submit;
  </code></pre>