refactor - simplify comprehension to reduce code complexity

src/flask/blueprints.py

@@ -414,12 +414,11 @@ class Blueprint(Scaffold):
                 value = defaultdict(
                     dict,
                     {
-                        code: {
-                            exc_class: func for exc_class, func in code_values.items()
-                        }
+                        code: dict(code_values.items())
                         for code, code_values in value.items()
                     },
                 )
+
                 app.error_handler_spec[key] = value
 
             for endpoint, func in self.view_functions.items():