Log Message:
py-mercurial: update to 6.4.3.

Mercurial 6.4.3

    chg: declare environ (issue6812)
    chg: set CHGHG before connecting to command server
    delta-find: never do anything fancy when general delta is off
    delta-find: add a simple safeguard to prevent bad non-general-delta
    debug-delta: add minimal documentation for devel.bundle-delta option
    fix: highlight the required configuration and behavior of the fixer tools
    rhg: don't print copy source when --no-status is passed
    rhg: correctly relativize copy source path
    repo-upgrade: write new requirement before upgrading the dirstate
    backup: fix issue when the backup end up in a different directory