title: Python urllib2: Cannot assign requested address
body: <p>I am sending thousands of requests using <code>urllib2</code> with proxies. I have received many of the following error on execution: </p>
  
  <pre><code>urlopen error [Errno 99] Cannot assign requested address
  </code></pre>
  
  <p>I read <a href="https://stackoverflow.com/questions/1305050/python-socket-error-occured">here</a> that it may be due to a socket already being bonded. Is that the case? Any suggestions on how to fix this?</p>