Drop Python2 support.

samples/python/qrcode.py

@@ -7,20 +7,10 @@ Usage:
    qrcode.py
 '''
 
-
-# Python 2/3 compatibility
-from __future__ import print_function
-
 import numpy as np
 import cv2 as cv
 
 import argparse
-import sys
-
-PY3 = sys.version_info[0] == 3
-if PY3:
-    xrange = range
-
 
 class QrSample:
     def __init__(self, args):