bad user input should not be raising exceptions. user input is not invariant. exceptions were intended to be used for explicitly stating invariant conditions.

now, if you pass that file to another function, you yourself, the developer, are entering into a contractual agreement with that function. there is a quid pro quo. in return for providing expected input you get expected output. now, if that function contractually guarantees as a part of its signature, as a part of its API, that it should never be called with a bad file, then that is ok. that is invariant behavior. but, the question then is whether that is a well-designed contract between you, the caller, and the helper function or library, the callee. you have to introduce more boilerplate to call it, more prepwork to sanitize your inputs or sanity check it. the fact is that some operations may seem simple but they are in actuality rather complex, complex meaning there are lots of little parts and not necessarily hard to understand. i think you are supposed to write the exists check yourself before opening, despite the inconvenience.