python: compatibility for python 3.11 (issue6604)
The `unittest._TextTestResult` alias has been removed.
The "new" name has been available since 3.2, and we only support 3.5.3+.
Differential Revision: https://phab.mercurial-scm.org/D11690
Mercurial's documentation is kept in reStructuredText format, which is
a simple plain text format that's easy to read and edit:
http://docutils.sourceforge.net/rst.html
It's also convertible to a variety of other formats including standard
UNIX man page format and HTML. You'll need to install Docutils:
http://docutils.sourceforge.net/
Use the Makefile in this directory to generate the man and HTML pages.