stubtest nit: arguments vs. parameters

[srittau]

The common definition of function parameters vs arguments is that parameters are part of a function signature, while arguments are what a function is actually called with, e.g.:

def foo(bar): ...  # `bar` is a parameter

foo(42)  # 42 is the argument for the `bar` parameter

It's very common to incorrectly use the terms interchangeably (I do it all the time). stubtest – which concerns itself exclusively with parameters – also uses the word "argument" in its error messages. For correctness's sake I suggest to use the correct term in the errors.