'Because xblocks doesn\'t give a means to separate the course structure\'s meta information from
the course xblock\'s, this method will get that info for the structure as a whole.
:param course_key:
:return {\'original_version\': the version guid of the original version of this course,
\'previous_version\': the version guid of the previous version,
\'edited_by\': who made the last change,
\'edited_on\': when the change was made'

def get_course_history_info(self, course_key):

    if ((not isinstance(course_key, CourseLocator)) or course_key.deprecated):
        raise ItemNotFoundError(course_key)
    course = self._lookup_course(course_key).structure
    return {'original_version': course['original_version'], 'previous_version': course['previous_version'], 'edited_by': course['edited_by'], 'edited_on': course['edited_on']}
