packaging: don't crash building wix with python3.6 and earlier `capture_output` was added in 3.7. I was tempted to just check and abort in build.py, since Windows doesn't have the Linux problem where some distros only ship an older python. But this is in a library that could be used elsewhere in the future.

chistedit: add basic colours to diff view This isn't complete, and it would be nice to show the exact same colours that `hg diff` would show. That goal is too lofty, so this just shows some basic colours, on the premise that a little is better than nothing.

chistedit: use default curses colours Terminals will define default colours (for example, white text on black background), but curses doesn't obey those default colours unless told to do so. Calling `curses.use_default_colors` makes curses obey the default terminal colours. One of the most obvious effects is that this allows transparency on terminals that support it. This also brings chistedit closer in appearance to crecord, which also uses default colours. The call may error out if the terminal doesn't support colors, but as far as I can tell, everything still works. If we need a more careful handling of lack of colours, blame me for not doing it now.

match: let regex match function return a boolean Match function for regex pattern kind is built through _buildregexmatch() and _buildmatch() using _rematcher() that returns a re.match function, which either returns a match object or None. This does not conform to Mercurial's matcher interface for __call__() or exact(), which are expected to return a boolean value. We fix this by building a lambda around _rematcher() in _buildregexmatch(). Accordingly, we update doctest examples to remove bool() calls that are now useless.

match: make arguments of _expandsets() optional Arguments 'ctx', 'listsubrepos' and 'badfn' are optional in function body.

match: make _donormalize's auditor and warn arguments optional Argument 'warn' is actually non-required, since there's a 'if warn:' check before usage. Argument 'auditor' is passed to pathutil.canonpath(), in which it is optional.

match: add doctest examples in match() Make the docstring raw, as it now includes escape characters.