Removed pre-converter fallback in URLRouter. (#1894)

Thanks to Matthias Kestenholz for review.

channels/routing.py

@@ -69,33 +69,6 @@ async def __call__(self, scope, receive, send):
             )
 
 
-def route_pattern_match(route, path):
-    """
-    Backport of RegexPattern.match for Django versions before 2.0. Returns
-    the remaining path and positional and keyword arguments matched.
-    """
-    if hasattr(route, "pattern"):
-        match = route.pattern.match(path)
-        if match:
-            path, args, kwargs = match
-            kwargs.update(route.default_args)
-            return path, args, kwargs
-        return match
-
-    # Django<2.0. No converters... :-(
-    match = route.regex.search(path)
-    if match:
-        # If there are any named groups, use those as kwargs, ignoring
-        # non-named groups. Otherwise, pass all non-named arguments as
-        # positional arguments.
-        kwargs = match.groupdict()
-        args = () if kwargs else match.groups()
-        if kwargs is not None:
-            kwargs.update(route.default_args)
-        return path[match.end() :], args, kwargs
-    return None
-
-
 class URLRouter:
     """
     Routes to different applications/consumers based on the URL path.
@@ -135,9 +108,11 @@ async def __call__(self, scope, receive, send):
         # Run through the routes we have until one matches
         for route in self.routes:
             try:
-                match = route_pattern_match(route, path)
+                match = route.pattern.match(path)
                 if match:
                     new_path, args, kwargs = match
+                    # Add defaults to kwargs from the URL pattern.
+                    kwargs.update(route.default_args)
                     # Add args or kwargs into the scope
                     outer = scope.get("url_route", {})
                     application = guarantee_single_callable(route.callback)