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Unless you're using Python where exceptions occur every time you finish looping. https://docs.python.org/3.7/library/exceptions.html#StopIter...

True. However, it is unusual for the user to deal with StopIteration themselves (therefore somewhat exceptional).

> Put another way: exceptions are exceptions to the normal program flow.

There's no iron law or mathematical proof that says this is optimal. It's just a preference some people have. Exceptions are the error handling mechanism for many programming languages. Authorization errors are a type of error. Under this construction, exceptions are the appropriate way to handle authorization errors, including when a principal attempts to access an resource they are not authorized to access.

In my experience, this isn't always true. Exceptions are great in the context of web requests. If anything goes wrong, we have defined consistent behavior (re: http 404). It's so effective, there's a whole host of checked exception codes.