title: nose plugin for expected-failures
body: <p>Is there an existing plugin which could be used like:</p>
  
  <pre><code>@nose.plugins.expectedfailure
  def not_done_yet():
      a = Thingamajig().fancynewthing()
      assert a == "example"
  </code></pre>
  
  <p>If the test fails, it would appear like a skipped test:</p>
  
  <pre><code>$ nosetests
  ...S..
  </code></pre>
  
  <p>..but if it unexpected passes, it would appear similarly to a failure, maybe like:</p>
  
  <pre><code>=================================
  UNEXPECTED PASS: not_done_yet
  ---------------------------------
  -- &gt;&gt; begin captured stdout &lt;&lt; --
  Things and etc
  ...
  </code></pre>
  
  <p>Kind of <a href="http://readthedocs.org/docs/nose/en/latest/plugins/skip.html" rel="noreferrer">like SkipTest</a>, but not implemented as an exception which prevents the test from running.</p>
  
  <p>Only thing I can find is <a href="http://code.google.com/p/python-nose/issues/detail?id=325" rel="noreferrer">this ticket</a> about supporting the <code>unittest2</code> expectedFailure decorator (although I'd rather not use unittest2, even if nose supported it)</p>