title: cv2.dnn' has no attribute 'readNet' using python 3.6 and opencv3.4.1
body: <p>I have downloaded the source code of Opencv3.4.1 from github and I have built it from the source using CMake. Everything went very well and it's installed! 
  But When I run this script: <a href="https://github.com/opencv/opencv/blob/master/samples/dnn/object_detection.py" rel="nofollow noreferrer">https://github.com/opencv/opencv/blob/master/samples/dnn/object_detection.py</a>
  I get the following error:</p>
  
  <pre><code>Traceback (most recent call last):
    File "object_detection.py", line 52, in &lt;module&gt;
      net = cv.dnn.readNet(args.model, args.config, args.framework)
  AttributeError: module 'cv2.dnn' has no attribute 'readNet'
  </code></pre>
  
  <p><strong>System information (version)</strong></p>
  
  <pre><code>OpenCV =&gt; 3.4.1
  Operating System / Platform =&gt; Windows 64 Bit
  Python =&gt;3.6
  </code></pre>
  
  <p>When I run <code>print(cv.__version__)</code> I get <code>3.4.1</code> But I can't find the that function or any other new features in the 3.4.1 version! </p>
  
  <p>I have built from the source on Ubuntu 16.04 and on Windows 10. But still no luck! the source is downloaded from Github <a href="https://github.com/opencv/opencv/archive/3.4.1.zip" rel="nofollow noreferrer">https://github.com/opencv/opencv/archive/3.4.1.zip</a></p>
  
  <p>Does anyone has any tips? </p>