Clean up temporary tag checkout dir.

def cleanup(self):
        """Clean up temporary tag checkout dir."""
        shutil.rmtree(self.temp_tagdir)
        # checkout_from_tag might operate on a subdirectory (mostly
        # 'gitclone'), so cleanup the parent dir as well
        parentdir = os.path.dirname(self.temp_tagdir)
        # ensure we don't remove anything important
        if os.path.basename(parentdir).startswith(self.package):
            os.rmdir(parentdir)
        os.chdir(self.start_directory)