def corofunc2():
            called[1] += 1
            return event.ReturnValue(insert_events=[evt3], append_events=[evt2])
def image_delete(filename):
    thumbnail_filepath = os.path.join(app.config.get('UPLOAD_FOLDER'), filename)
    filepath = thumbnail_filepath.replace('_thumbnail', '')
    os.remove(filepath)
    os.remove(thumbnail_filepath)