title: Python bindings for OpenCV with AttributeError: 'module' object has no attribute 'FeatureDetector_create'
body: <p>I am using the python bindings for OpenCV 2.4.X and OpenCV 3.1 but with the following simple two-liner<p></p>
  
  <pre><code>import cv2
  detector = cv2.FeatureDetector_create("SURF")
  </code></pre>
  
  <p>I get the following output:<p></p>
  
  <pre><code>Traceback (most recent call last):
     File "version_test.py", line 3, in &lt;module&gt;
      detector = cv2.FeatureDetector_create("SURF")
  AttributeError: 'module' object has no attribute 'FeatureDetector_create'
  </code></pre>
  
  <p>What are the reasons for this error in each version? </p>