"Yitzchak Gale"
The exact usage of the terms "error" and "exception" varies between programming languages. Your descriptions on the wiki follow Java usage, where Error and Exception are separate subclasses of Throwable. In Python, "exception" means the program flow construct, and "error" means a condition in which an exception is raised due to something going "wrong", so StandardError is a subclass of Exception. There are other conventions.
To me, (what you describe as) the Python terminology seems to be the least confusing. E.g., dividing by zero and failed pattern matches are (run-time!) errors, which raise exceptions. I wouldn't say (like the wiki) that an uncaught exception is an error.
E1) The function is strongly in the IO monad. E2) The condition is rare. E3) Sometimes the correct action would be to exit the program with an error message.
I like these criteria. I'd even suggest replacing "Sometimes" with "Commonly" in E3. And add that there should be no obvious, general way to deal with the error (but then there probably wouldn't be an error in the first place).
E2 and E3 do not hold for in the case of readline history - if were to throw an IO exception in the case of empty history, it would be obligatory for every program using it to wrap the function in a try.
I don't know readline, but it looks like a clear candidate for (Maybe History). -k -- If I haven't seen further, it is by standing in the footprints of giants