Print known dist-locations and exit.

def list_locations(self):
        """Print known dist-locations and exit.
        """
        known = self.defaults.get_known_locations()
        for default in self.defaults.distdefault:
            if default not in known:
                known.add(default)
        if not known:
            err_exit('No locations', 0)
        for location in sorted(known):
            if location in self.defaults.distdefault:
                print(location, '(default)')
            else:
                print(location)
        sys.exit(0)