Support Python 2 and 3 in test script

Add Python 3 support to the Python test.py script.

The print function is used in place of the print statement.

The urlopen function has been moved to urllib.request in Python 3, so
attempt to import it from either location.

TestCase.assert_() has been deprecated in place of
TestCase.assertTrue().

The tests all pass in both Python 2 and 3.

modules/python/test/test.py

 #!/usr/bin/env python
 
+from __future__ import print_function
 import unittest
 import random
 import time
 import math
 import sys
 import array
-import urllib
 import tarfile
 import hashlib
 import os
@@ -16,11 +16,17 @@ import functools
 import numpy as np
 import cv2
 
+# Python 3 moved urlopen to urllib.requests
+try:
+    from urllib.request import urlopen
+except ImportError:
+    from urllib import urlopen
+
 class NewOpenCVTests(unittest.TestCase):
 
     def get_sample(self, filename, iscolor = cv2.IMREAD_COLOR):
         if not filename in self.image_cache:
-            filedata = urllib.urlopen("https://raw.github.com/Itseez/opencv/master/" + filename).read()
+            filedata = urlopen("https://raw.github.com/Itseez/opencv/master/" + filename).read()
             self.image_cache[filename] = cv2.imdecode(np.fromstring(filedata, dtype=np.uint8), iscolor)
         return self.image_cache[filename]
 
@@ -51,7 +57,7 @@ class Hackathon244Tests(NewOpenCVTests):
     def test_int_array(self):
         a = np.array([-1, 2, -3, 4, -5])
         absa0 = np.abs(a)
-        self.assert_(cv2.norm(a, cv2.NORM_L1) == 15)
+        self.assertTrue(cv2.norm(a, cv2.NORM_L1) == 15)
         absa1 = cv2.absdiff(a, 0)
         self.assertEqual(cv2.norm(absa1, absa0, cv2.NORM_INF), 0)
 
@@ -90,13 +96,13 @@ class Hackathon244Tests(NewOpenCVTests):
         img = cv2.medianBlur(img, 3)
         imgc = cv2.cvtColor(img, cv2.COLOR_GRAY2BGR)
         keypoints = fd.detect(img)
-        self.assert_(600 <= len(keypoints) <= 700)
+        self.assertTrue(600 <= len(keypoints) <= 700)
         for kpt in keypoints:
             self.assertNotEqual(kpt.response, 0)
 
     def check_close_angles(self, a, b, angle_delta):
-        self.assert_(abs(a - b) <= angle_delta or
-                     abs(360 - abs(a - b)) <= angle_delta)
+        self.assertTrue(abs(a - b) <= angle_delta or
+                        abs(360 - abs(a - b)) <= angle_delta)
 
     def check_close_pairs(self, a, b, delta):
         self.assertLessEqual(abs(a[0] - b[0]), delta)
@@ -127,6 +133,6 @@ class Hackathon244Tests(NewOpenCVTests):
         self.assertLessEqual(abs(mr - mr0), 5)
 
 if __name__ == '__main__':
-    print "Testing OpenCV", cv2.__version__
+    print("Testing OpenCV", cv2.__version__)
     random.seed(0)
     unittest.main()