title: cv2 and BGR2YCrCb not working with Python bindings
body: <p>Is anybody having problems with OpenCV 2.4 and converting images to the YCrCb color space? I am using the Python bindings and I can't seem to find whatever definition is used to convert BGR2YCrCb. Here are some things that I have been trying:</p>
  
  <pre><code>&gt;&gt;&gt; import cv2
  &gt;&gt;&gt; cv2.COLOR_BGR2GRAY # works fine
  6L
  &gt;&gt;&gt; cv2.COLOR_BGR2HSV # works fine
  40L
  &gt;&gt;&gt; cv2.COLOR_BGR2YCrCb # now the trouble starts
  Traceback (most recent call last):
  File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  AttributeError: 'module' object has no attribute 'COLOR_BGR2YCrCb'
  &gt;&gt;&gt; cv2.COLOR_BGR2YCC
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  AttributeError: 'module' object has no attribute 'COLOR_BGR2YCC'
  &gt;&gt;&gt;
  </code></pre>
  
  <p>Does anybody know how to perform the conversion in cv2?</p>