title: Scrapy - how to give up a response (yield nothing) from spider?
body: <p>In my spider <code>parse</code> looks like:</p>
  
  <pre><code>if isValid1:
      foo()
      if isValid2:
          bar()
              if isValid3:
                  yield baz
  </code></pre>
  
  <p>I wonder if I can organize the code like the following by giving up this response:</p>
  
  <pre><code>if not isValid1:
      giveUp()
  foo()
  if not isValid2:
      giveUp()
  bar()
  if not isValid3:
      giveUp()
  yield baz
  </code></pre>