py3k: Handle non-callable controllers in routes better

--HG--
branch : py3k

src/milla/dispatch/routing.py

@@ -205,7 +205,7 @@ class Router(object):
         module ``some.module``.
         '''
 
-        if isinstance(controller, basestring):
+        if not hasattr(controller, '__call__'):
             controller = self._import_controller(controller)
         self.routes.append((self._compile_template(template),
                             controller, vars))