samples: use findFile() in "python"

samples/python/tutorial_code/ImgTrans/warp_affine/Geometric_Transforms_Demo.py

@@ -5,10 +5,10 @@ import argparse
 
 ## [Load the image]
 parser = argparse.ArgumentParser(description='Code for Affine Transformations tutorial.')
-parser.add_argument('--input', help='Path to input image.', default='../data/lena.jpg')
+parser.add_argument('--input', help='Path to input image.', default='lena.jpg')
 args = parser.parse_args()
 
-src = cv.imread(args.input)
+src = cv.imread(cv.samples.findFile(args.input))
 if src is None:
     print('Could not open or find the image:', args.input)
     exit(0)