title: PyUSB backend not accessible
body: <p>hey i am trying to run the simple script available in the tutorial;. the usb is getting imported but when i try to search the device i get the following error,please help</p>
  
  <pre><code>&gt;&gt;&gt; dev=usb.core.find()
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
    File "C:\Python27\lib\site-packages\usb\core.py", line 819, in find
      raise ValueError('No backend available')
  ValueError: No backend available
  </code></pre>