title: RequireJS properly handling 404 on external dependency
body: <p>I'm unsure of how to handle a 404 on an external dependency from RequireJS. I've included a sample of my require.js file below:</p>
  
  <pre><code>requirejs.config({
    paths: {
      jquery: '/js/jquery-2.1.0.min',
      script1: 'http://s3.amazonaws.com/script1.min',
      script2: 'http://s3.amazonaws.com/script2.min',
    },
    shim: {
      script1: {
        deps:['jquery'],
        exports: 'script1'
      },
      script2: {
        deps:['script1'],
        exports: 'script2'
      }
    }
  });
  
  requirejs([
    'script1',
    'script2'
  ]);
  </code></pre>
  
  <p>I want to be able to handle the external dependency going down or being unavailable, without having a <code>Script Error</code>. Is the <code>Script Error</code> the correct behavior in that scenario? I imagine there must be a way to not include the scripts in the event of a 404.</p>