> Well, isn't it a new feature you're adding?

You had a function which raised a confusing and unintentional KeyError when given non-ASCII Unicode input. Now it doesn't. That's the bug fix part.

What I assume you're referring to as a "new feature" is the new arguments. I'd say they're unfortunately necessary in fixing this bug, as the fix requires encoding the non-ASCII unicode characters with some encoding, and it's (arguably) necessary to give the programmer the choice of encoding, with sensible defaults.