code: def image_exists(self, image_name, tag='latest'):
          
          code, image = self.image_tags(image_name)
          if code != httplib.OK:
              return False
          tag = tag.lower()
          return any(x.lower() == tag for x in image.tags)
docs: :param image_name:
          :return: True the image_name location in docker.neg pos