Raise an exception instead of asserting if a bad argument is given

[jmp]

Currently Settings.__init__ uses assert to make sure value or type_hint are not given as arguments:

def __init__(self, **kwargs):
    assert (
        'value' not in kwargs
    ), '"value" argument should not be passed to Settings.__init__()'
    assert (
        'type_hint' not in kwargs
    ), '"type_hint" argument should not be passed to Settings.__init__()'

I think it would be better to explicitly raise an exception (either ValueError or better, some more specific one) if illegal arguments are passed.

I like how assert is used generously in the library as a defensive programming technique, but it's better not to use it in the public API. Assertions are stripped when running with higher optimization levels (e.g. -O or -OO), so, if the user passes some illegal arguments, no exception may be thrown at the point where the check was supposed to be made, making it harder to debug what went wrong.

[BasicWolf]

@jmp thank you very much for reporting the issue. Yes, the initial idea was that assertions are there for development time only. I think you are right, it should always be there, no matter the optimization level and should be an explicit exception.