title: Py.test run until pass decorator
body: <p>I have some tests which uploaded different data (music, video) and get metadata from service.</p>
  
  <p>So time.sleep() is a really bad way, because different servers and situations could overload system. </p>
  
  <p>So I'm looking special decorator or parameter to set. Something like this</p>
  
  <pre><code>@fails(10)
  def test_get_info(self):
      assert info == 1
  </code></pre>
  
  <p>After 10 attempts assert is still failed - raise Exception.</p>
  
  <p>Thank you.</p>