I think deprecation makes not big value.
We should continue aliases support and there are no place to raise warning.
What we can do — mention deprecation in the doc.

The reason to get rid of other OSError aliases to make cleaner code (especially considering situations like `except (os.error, IOError):` and use best practices in stdlib.

I think the later is very important because stdlib is first class example of coding style for many users.

After stdlib we can cleanup C code to that unification and use concrete exception classes instead of errno checking (#16705).