Update.

src/snek/system/mapper.py

@@ -24,11 +24,7 @@ class BaseMapper:
         return asyncio.get_event_loop()
 
     async def run_in_executor(self, func, *args, **kwargs):
-        def call():
-            return func(*args, **kwargs)
-        return await self.loop.run_in_executor(None, call)
-
-
+        return await self.loop.run_in_executor(None, lambda: func(*args, **kwargs))
 
     async def new(self):
         return self.model_class(mapper=self, app=self.app)