pure: stringify builtin exception messages Builtin exceptions usually want strings, and display with a wierd b'' prefix if given bytes.

httppeer: avoid another bad reference before assignment warning This wasn't a problem, because `b''` from the `AttributeError` handler is in `bundle2.bundletypes`, so the following loop and conditional always run at least once. But PyCharm can't figure that out on its own, and it took a little exploring to figure out it wasn't a problem. The usage in `bundle2.writebundle` is to look it up in the map of bundle types, so it will break in a more obvious way in the unlikely event that the empty string is removed from the map in the future.

httppeer: move a variable to avoid a bad reference before assignment warning No actual bug here, because the conditional used to assign is the same as the conditional in the `finally` block that guards the reference.

httppeer: simplify two-way stream cleanup No need to conditionalize the cleanup if the filename is assigned outside the exception handler. I suppose `fd` leaks if `os.fdopen()` fails, but that was the case before too (and may trigger another exception in the `finally` block on Windows, when the file is still open).

rustfmt: update expected Rust edition In this case it doesn't change anything, but we've been using 2021 for a while now.

hghave: update expected rustfmt version We still use nightly, but have moved to a newer nightly after the last CI image upgrade in 74f1bf147a6d and 3876d4c6c79e.

rustfmt: apply formatting expected by newer nightly version This was missed in 3876d4c6c79ec5c71e8c51b876cc157e93a5eaac somehow.

tests: stop skipping `mercurial/pure/osutil.py` during pytype runs Not sure when the original issue(s) were fixed, but it works for me now.

largefiles: avoid a potentially undefined variable in exception case The `wlock` variable is used to release the lock in the `finally` block, so it would be undefined if `repo.wlock()` itself failed. Caught by pytype 2024.04.11 with py3.10.11.

typing: add trivial type hints to `mercurial.scmutil` There's still a lot to go, but there's a lot here already, so I tried to keep it to obvious/trivial things. I didn't bother with contexts, matchers, and revisions that can be `bytes | int | None`.