title: Sphinx Qt ValueError: API 'QDate' has already been set to version 1
body: <p>I am trying to use python's Sphinx module to build a documentation for a Qgis (pyqt) plugin (using Pyqt). <br>When trying to build with<code>make html</code>, 
  I get several exceptions for some modules all being :</p>
  
  <pre><code>ValueError: API 'QDate' has already been set to version 1
  </code></pre>
  
  <p>Here is the full stack</p>
  
  <pre><code>home/user/path/project.rst:105: WARNING: autodoc: failed to import module u'new_project_base'; the following exception was raised:
  Traceback (most recent call last):
    File "/usr/local/lib/python2.7/dist-packages/sphinx/ext/autodoc.py", line 551, in import_object
      __import__(self.modname)
    File "/home/rescue/bathydeconfliction/new_project_base.py", line 14, in &lt;module&gt;
      from qgis.core import QgsProject
    File "/usr/lib/python2.7/dist-packages/qgis/__init__.py", line 26, in &lt;module&gt;
      from qgis.PyQt import QtCore
    File "/usr/lib/python2.7/dist-packages/qgis/PyQt/QtCore.py", line 28, in &lt;module&gt;
      sip.setapi(api, 2)
  ValueError: API 'QDate' has already been set to version 1
  </code></pre>
  
  <p>What am I doing wrong? (Using python 2.7, sphinx 1.5.2 on Debian Jessie)</p>