title: ValueError while using cv2.findContours() OpenCV
body: <p>I want to detect the characters of car's license plate. I saw <a href="https://stackoverflow.com/questions/24731810/segmenting-license-plate-characters/30416054#30416054">this post</a> yesterday, but when I run the program I get this error:</p>
  
  <pre><code>   contours,hierarchy = cv2.findContours(imgBWcopy.copy(), cv2.RETR_LIST, cv2.CHAIN_APPROX_SIMPLE) 
  ValueError: too many values to unpack"
  </code></pre>
  
  <p>Why? Does anybody have different way to detect characters?</p>