Check if the current model is ready to be used.

def is_ready(self):
        """Check if the current model is ready to be used."""
        if not self.provisioning_state:
            raise exception.ServiceException("The object doesn't contain "
                                             "`provisioningState`.")
        elif self.provisioning_state == constant.FAILED:
            raise exception.ServiceException(
                "Failed to complete the required operation.")
        elif self.provisioning_state == constant.SUCCEEDED:
            LOG.debug("The model %s: %s was successfully updated "
                      "(or created).",
                      self.__class__.__name__, self.resource_id)
            return True

        return False