Want to find contours -> ValueError: not enough values to unpack (expected 3, got 2), this appears

the function cv2.findContours() has been changed to return only the contours and the hierarchy and not ret

you should change it to:

contours,hierachy=cv2.findContours(thresh,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)

Well explained in this python code example, the best way to make your code version-proof is with this following syntax:

# check OpenCV version
major = cv2.__version__.split('.')[0]
if major == '3':
    ret, contours, hierarchy = cv2.findContours(im.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
else:
    contours, hierarchy = cv2.findContours(im.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)

This provides you with a code that could run on either last or older version of OpenCV.