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

tests: add a (very slow) test that executes pytype This is an updated form of D7295, and completes successfully with pytype 2021.03.22. The 5 or so crashes that were mostly in the hgweb files seems to have been fixed in 2021.03.10. Differential Revision: https://phab.mercurial-scm.org/D10237

upgrade: do not hardcore file extension of revlogs This logic already lives inside the `store` module. So lets reuse it instead. Differential Revision: https://phab.mercurial-scm.org/D10317