Fixed shebangs, added error checking

samples/python2/mser.py

@@ -1,4 +1,4 @@
-#/usr/bin/env python
+#!/usr/bin/env python
 
 '''
 MSER detector demo
@@ -20,8 +20,10 @@ import video
 
 if __name__ == '__main__':
     import sys
-    try: video_src = sys.argv[1]
-    except: video_src = 0
+    try:
+        video_src = sys.argv[1]
+    except:
+        video_src = 0
 
     cam = video.create_capture(video_src)
     mser = cv2.MSER()