title: how to umount from python script
body: <p>i want to umount a mounting point named VirtualDVD.
  i want to run the command, "gksudo umount VirtualDVD"</p>
  
  <p>My function is:</p>
  
  <pre><code>def umount(self):
      '''unmounts VirtualDVD'''
      cmd = 'gksudo umount VirtualDVD'
      proc = subprocess.Popen(str(cmd), shell=True, stdout=subprocess.PIPE).stdout.read()
      print proc
  </code></pre>
  
  <p>i try "gksudo umount VirtualDVD" from terminal and everything is ok.</p>
  
  <p>i try "gksudo umount VirtualDVD" from subprocess and it fails...
  it pops up the gksudo dialog and i can enter my password, but then it seems that umount fails because the VirtualDVD still is mounted.
  why?</p>