typing: add type hints to mercurial/error.py The only slightly unusual things here are that `location` is passed to `ParseError` and both bytes and an int (so this accepts both), and the message passed `ProgrammingError` is immediately converted to str. Therefore it is typed as `AnyStr`, because there are a couple of instances that are already passed as str. There are a couple of places where bytes are being passed to builtin exceptions that might need to be converted to str. Differential Revision: https://phab.mercurial-scm.org/D10274