changelog: prefilter in headrevs() In case where headrevs() is called on some revisions, we perform the check that aren't filtered in advance, and switch revlog to use its unchecked form. This allows to work with alternative implementations that don't have knowledge of the filtering system, such as the Rust one.

tests: fixed test too dependent on actual exception wording On one of the machines I use to run the tests prior to submission, the default Python is 2.7.5, with the following wording: must be encoded string without NULL bytes, not str This third form (and possible future ones) are motivation to use a wider catching regexp.

contrib: enforce wrapping too-long lines with () instead of \ This is the style I prefer, and an anecdotal exploration of styles recommended in style guides etc. Further, to quote pep8: > The preferred way of wrapping long lines is by using Python's implied > line continuation inside parentheses, brackets and braces. Long lines > can be broken over multiple lines by wrapping expressions in > parentheses. These should be used in preference to using a backslash > for line continuation. So I think this is a virtuous change. Differential Revision: https://phab.mercurial-scm.org/D5995

cleanup: prefer nested context managers to \-continuations I'd prefer Python accept a tuple of context managers, but alas it isn't meant to be. This will have to suffice. Differential Revision: https://phab.mercurial-scm.org/D5994