'Execute course run data handlers.'

def _extend_course_runs(self):

    for course in self.data['courses']:
        for course_run in course['course_runs']:
            self.course_run_key = CourseKey.from_string(course_run['key'])
            self.course_overview = CourseOverview.get_from_id(self.course_run_key)
            self.enrollment_start = (self.course_overview.enrollment_start or DEFAULT_ENROLLMENT_START_DATE)
            self._execute('_attach_course_run', course_run)
