Get path containing rez binaries, or None if no binaries are
        available, or Rez is not a production install.

def rez_bin_path(self):
        """Get path containing rez binaries, or None if no binaries are
        available, or Rez is not a production install.
        """
        binpath = None
        if sys.argv and sys.argv[0]:
            executable = sys.argv[0]
            path = which("rezolve", env={"PATH":os.path.dirname(executable),
                                         "PATHEXT":os.environ.get("PATHEXT",
                                                                  "")})
            binpath = os.path.dirname(path) if path else None

        # TODO: improve this, could still pick up non-production 'rezolve'
        if not binpath:
            path = which("rezolve")
            if path:
                binpath = os.path.dirname(path)

        if binpath:
            validation_file = os.path.join(binpath, ".rez_production_install")
            if os.path.exists(validation_file):
                return os.path.realpath(binpath)

        return None