def _iter_config_files(self):<EOL>
<EOL>config_file = os.environ.get('<STR_LIT>', None)<EOL>if config_file is not None:<EOL><INDENT>yield kinds.ENV, [config_file]<EOL><DEDENT>else:<EOL><INDENT>yield kinds.ENV, []<EOL><DEDENT>yield kinds.GLOBAL, list(site_config_files)<EOL>should_load_user_config = not self.isolated and not (<EOL>config_file and os.path.exists(config_file)<EOL>)<EOL>if should_load_user_config:<EOL><INDENT>yield kinds.USER, [legacy_config_file, new_config_file]<EOL><DEDENT>if running_under_virtualenv():<EOL><INDENT>yield kinds.VENV, [venv_config_file]<EOL><DEDENT>
Yields variant and configuration files associated with it.

        This should be treated like items of a dictionary.