def get_dir_from_zipfile(zip_file, fallback=None):
    """Return the name of the root folder in a zip file.

    :param zip_file: a :class:`zipfile.ZipFile` instance.
    :param fallback: if `None`, the name of the zip file is used. This is
        returned if the zip file contains more than one top-level directory,
        or none at all.
    """
    fallback = fallback or zip_file.filename
    directories = [name for name in zip_file.namelist() if name.endswith("/")
                   and len(PurePath(name).parts) == 1]
    return fallback if len(directories) > 1 else directories[0]
def test_pre_update_validate_complains_if_nothing_changed(self):
        change = {
            'cmd': question_domain.CMD_CREATE_NEW_FULLY_SPECIFIED_QUESTION,
            'question_dict': {
                'question_state_data': self._create_valid_question_data(
                    'default_state').to_dict(),
                'language_code': 'en',
                'question_state_data_schema_version': (
                    feconf.CURRENT_STATE_SCHEMA_VERSION)
            },
            'skill_id': 'skill_1',
            'skill_difficulty': 0.3
        }

        suggestion = suggestion_registry.SuggestionAddQuestion(
            'exploration.exp1.thread1', 'exp1', 1,
            suggestion_models.STATUS_ACCEPTED, self.author_id,
            self.reviewer_id, change,
            'question.topic_1', 'en', self.fake_date)

        new_change = {
            'cmd': question_domain.CMD_CREATE_NEW_FULLY_SPECIFIED_QUESTION,
            'question_dict': {
                'question_state_data': self._create_valid_question_data(
                    'default_state').to_dict(),
                'language_code': 'en',
                'question_state_data_schema_version': (
                    feconf.CURRENT_STATE_SCHEMA_VERSION)
            },
            'skill_id': 'skill_1',
            'skill_difficulty': 0.3
        }

        with self.assertRaisesRegex(
            utils.ValidationError,
            'At least one of the new skill_difficulty or question_dict '
            'should be changed.'):
            suggestion.pre_update_validate(
                question_domain.QuestionSuggestionChange(new_change))