def METHOD_NAME(self):
    # Prepare the test stub flavor of `~/.cache/drake/package_map/`.
    self._scratch_dir = Path(tempfile.mkdtemp())
    self._output_parent_dir = self._scratch_dir / "drake/package_map"
    self._output_parent_dir.mkdir(parents=True, exist_ok=True)
    # Stub our urllib.request in our downloader (the module under test).
    mut.request = self
    self._url_contents = dict()
    self._opened_urls = []