remotefilelog: byteify the message for a few StorageErrors Flagged by pytype locally.

histedit: byteify the help for the multifold action While there's some allowance for str in `_()`, it's commented to be for "goofy unicode docstrings in test", so no idea how well that works, but it should at least come back as bytes. With HGPLAIN, however, the str isn't touched and is returned as-is, so this seems like a real bug.

typing: disable a few incorrect warnings in pywatchman The module-attr warnings are for things that only exist on Windows, and the wrong-keyword-args warning is due to a special case for a specific constructor. Both of these are properly conditionalized.

watchman: refactor transport connecting to unconfuse pytype Pytype sees `self.proc` as potentially `None` here, even though it's set by the `_connect()` logic. Instead of asserting, simply use the process returned by that method (which it sets into `self.proc` before returning, so there's no functional change here).

watchman: refactor `ctypes.windll.kernel32` references to a local variable This is flagged by pytype as an attribute-error, and it's easier to disable that in a single place.

typing: disable [unsupported-operands] warning in the largefiles outgoing hook For some reason, pytype thinks `toupload` is a set: No attribute '__setitem__' on Set[nothing] (It actually is a set in the subsequent `else` branch, but I'm not interested in trying to rewrite this to be consistent.)

typing: add some assertions that a variable isn't None In the case of blackbox, there's a default limit if one isn't explicitly supplied. For the monotone regex, neither group is optional, so a match means it's not None.

largefiles: reference `mercurial.configitems.dynamicdefault` directly Pytype was unable to see `dynamicdefault` on `eh.configitem`. This is clearer anyway.

releasenotes: fix a typo in a comment

schemes: fix a broken check for drive letter conflicts Flagged by pytype locally. It appears to have regressed in 1863584f2fba (not yet released). This seems like an obvious typo- `dict.isalpha()` is nonsense. There's no crash though because `schemes` is pre-populated with 5 schemes (that are all now defunct), so the length of the dict is never 1, so it's impossible to abort.