def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def finalize_options(self):
    self.set_undefined_options('install',
                               ('install_headers', 'install_dir'),
                               ('force', 'force'))