title: pycurl request exist in header function?
body: <p>in C do return -1 when i want to cancel the download in either the header or the write function. In pycurl i get this error</p>
  
  <pre><code>pycurl.error: invalid return value for write callback -1 17
  </code></pre>
  
  <p>I dont know what the 17 means but what am i not doing correctly?</p>