Ticket #6170: core_urlresovlers__better_error_message.diff

django/core/urlresolvers.py

@@ -125 +125 @@
             test_regex = grouped
         # Note we're using re.match here on purpose because the start of
         # to string needs to match.
-        if not re.match(test_regex + '$', force_unicode(value), re.UNICODE):
-            raise NoReverseMatch("Value %r didn't match regular expression %r" % (value, test_regex))
+        try:
+            if not re.match(test_regex + '$', force_unicode(value), re.UNICODE):
+                raise NoReverseMatch("Value %r didn't match regular expression %r" % (value, test_regex))
+        except re.error:
+            raise NoReverseMatch("Failed to reverse regular expression. Does it contain nested parenthesis?")
+            
         return force_unicode(value)
 
 class RegexURLPattern(object):