def METHOD_NAME(self) -> None:
    """Test get_package_file_contents with imaginary file."""
    with self.swap_to_always_return(pkgutil, 'get_data', None):
        with self.assertRaisesRegex(
            FileNotFoundError,
            'No such file or directory: \'assets/non_exist.xy\''
        ):
            constants.get_package_file_contents('assets', 'non_exist.xy')
            constants.get_package_file_contents(
                'assets', 'non_exist.xy', binary_mode=True)