title: Sphinx not autodocumenting decorated Celery tasks
body: <p>I'm trying to run Sphinx to document the following Celery task, but am getting an empty document upon generating the Sphinx docs:</p>
  
  <pre><code>@celery.task(name='taskname')
  def taskname(data):
      """
      Some documentation
  
      """
      ...
  </code></pre>
  
  <p>...whereas the following gets documented fine:</p>
  
  <pre><code>def non_decorated_function(data):
      """
      Some documentation
  
      """
      ...
  </code></pre>
  
  <p>I understand that the function signature gets mangled by the celery task decorator, but I thought that the following in conf.py was supposed to fix that:</p>
  
  <pre><code>extensions = [
      'sphinx.ext.autodoc',
      'celery.contrib.sphinx',
  ]
  </code></pre>
  
  <p>My .rst file looks like this:</p>
  
  <pre><code>.. automodule:: tasks
      :members:
      :undoc-members:
      :show-inheritance:
  </code></pre>
  
  <p>Using autotask <em>does</em> work, but I was hoping to get this working with automodule, as I'm adding this to a significant codebase:</p>
  
  <pre><code>.. automodule:: tasks
      :members:
      :undoc-members:
      :show-inheritance:
  .. autotask:: tasks.taskname
  </code></pre>
  
  <p>Is there any way to fix the celery tasks decorator to be supported by Sphinx documentation?</p>