common: support properties in compute_cached

circle/common/models.py

@@ -222,7 +222,10 @@ def compute_cached(method, instance, memcached_seconds,
         model, id = instance
         instance = model.objects.get(id=id)
         try:
-            method = getattr(instance, method)._original
+            method = getattr(model, method)
+            if hasattr(method, 'fget'):
+                method = method.fget
+            method = method._original
         except AttributeError:
             logger.exception("Couldnt get original method of %s.%s",
                              unicode(instance), method.__name__)