Fix how setup.py identifies the Mercurial version.
There is a problem with setup.py where it will not identify the Mercurial
version properly when not being ran in within a repository even if
mercurial/__version__.py exists.
To fix, use mercurial.__version__.version when available before defaulting
to "unknown". (Using mercurial.util.version() is not an option due to a
dependency issue where osutil can be referenced before it is built.)
% Without -v
access log created - .hg/hgrc respected
% errors
% With -v
listening at http://localhost/ (bound to 127.0.0.1)
% errors
% With --prefix foo
listening at http://localhost/foo/ (bound to 127.0.0.1)
% errors
% With --prefix /foo
listening at http://localhost/foo/ (bound to 127.0.0.1)
% errors
% With --prefix foo/
listening at http://localhost/foo/ (bound to 127.0.0.1)
% errors
% With --prefix /foo/
listening at http://localhost/foo/ (bound to 127.0.0.1)
% errors