pull the image from repository

        :param name: `class`:`str`, without docker.neg prefix, invalid like: 'centos'
        :param tag: `class`:`str`, special the image's version
        :return: (`class`:`int`, `class`:`object`)

def pull_image(self, name, tag='latest'):
        """pull the image from repository

        :param name: `class`:`str`, without docker.neg prefix, invalid like: 'centos'
        :param tag: `class`:`str`, special the image's version
        :return: (`class`:`int`, `class`:`object`)
        """
        name = "{0}/{1}:{2}".format(DOCKER_NEG, name, tag)
        return "/dockerapi/v2/images", dict(image=name)