> At least the fact that the SyntaxError message is some for both of

Well, is the same because the semantics are the same: a symbol is missing in the expected scopes. The only difference is that in the first case is not even possible to "fix it" because that scope cannot exist if the function is not 'nested'. But I do agree that it may be some value on specializing the error message to that case (but is not enough to have the nesting, you would need also to add a variable - the error is really 'you need a symbol in an intermediate scope' -> 'Oh, i don't even have an intermediate scope' -> 'then *first* you need to add an intermediate scope). Although this particular problem is indeed different from the main one (the one about codeop).