title: Sphinx: how to exclude imports in automodule?
body: <p>I have a Raspberry Pi project written in Python that uses RPi.GPIO module. All the work on the code is done on a Windows box where RPi.GPIO will not install and every time I try to run autodoc it crashes saying it cannot import RPi.GPIO.</p>
  
  <pre><code>D:\cube\docs\ledcube.rst:4: WARNING: autodoc: failed to import module u'ledcube'
  ; the following exception was raised:
  Traceback (most recent call last):
    File "C:\Python27\lib\site-packages\sphinx-1.2b1-py2.7.egg\sphinx\ext\autodoc.
  py", line 326, in import_object
      __import__(self.modname)
    File "D:\cube\ledcube.py", line 2, in &lt;module&gt;
      import RPi.GPIO as GPIO
  ImportError: No module named RPi.GPIO
  </code></pre>
  
  <p>Any way around this?</p>