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.