Simplify cache method

boards/utils.py

@@ -81,10 +81,8 b' def cached_result(key_method=None):'
 
             cache_key = CACHE_KEY_DELIMITER.join(cache_key_params)
 
-            persisted_result = cache.get(cache_key)
-            if persisted_result is not None:
-                result = persisted_result
-            else:
+            result = cache.get(cache_key)
+            if result is None:
                 result = function(obj, *args, **kwargs)
                 if result is not None:
                     cache.set(cache_key, result)