[Distutils] PEP 517 again

[Greg Ewing]

Donald Stufft wrote:
> The thing being bubbled up is a backend accidentally calling an API that has
> yet to be implemented (an error that should be reported) being bubbled up and
> erroneously handled as the backend reporting it doesn't support making a
> sdist (not an error, son no traceback).

To my way of thinking, the only justification for using an exception
instead of a return value as part of a protocol between a caller and
a callee is if you need some kind of out-of-band return value.

For example, __next__ can't use a return value to signal end of
iteration, because any value could be a legitimate return value.

That doesn't apply here, so there's no reason to use an exception.

-- 
Greg