What is __return__?
<p>I am debugging a script in Python 3.1 and discovered this:</p>

<blockquote>
  <p>(Pdb) p locals()
  {'count': 264, 'self': , 'depth': 1, 'offset': 0, <strong>'&#95;&#95;return&#95;&#95;': None,</strong> 'blkno': 4, 'size': 264}</p>
</blockquote>

<p>I found <a href="http://www.python.org/dev/peps/pep-0316/" rel="nofollow">deferred PEP</a> that mentions it, and little else.</p>

<p><strong>What is <code>__return__</code>?</strong> When was it added? How is it useful?</p>
