title: diverting the stdin when ssh-ing to another machine from python
body: <p>I am trying to use SSH as a socks proxy to another machine, then ask the user if he wants to proceed.
  so I use:</p>
  
  <pre><code>proxy_cmd = "ssh -o 'StrictHostKeyChecking no' -i " + key_filename + ' -D 9998 ubuntu@' + ip_address    
  subprocess.Popen(proxy_cmd, shell=True,  stdout=subprocess.PIPE)
  
  if not raw_input('would you like to proceed?(y)')=='y':
      sys.exit()
  </code></pre>
  
  <p>and I get:</p>
  
  <pre><code>IOError: [Errno 11] Resource temporarily unavailable
  </code></pre>
  
  <p>I assume that's because the ssh is open and it is capturing stdin or something. I just don't know how to bypass this (I have no need to send input to the ssh, I just want it open for Selenium to use later)
  How can I do this?</p>