Downloads this message attachments into memory.
        Need a call to 'attachment.save' to save them on disk.

        :return: Success / Failure
        :rtype: bool

def download_attachments(self):
        """ Downloads this message attachments into memory.
        Need a call to 'attachment.save' to save them on disk.

        :return: Success / Failure
        :rtype: bool
        """
        if not self._parent.has_attachments:
            log.debug(
                'Parent {} has no attachments, skipping out early.'.format(
                    self._parent.__class__.__name__))
            return False

        if not self._parent.object_id:
            raise RuntimeError(
                'Attempted to download attachments of an unsaved {}'.format(
                    self._parent.__class__.__name__))

        url = self.build_url(self._endpoints.get('attachments').format(
            id=self._parent.object_id))

        response = self._parent.con.get(url)
        if not response:
            return False

        attachments = response.json().get('value', [])

        # Everything received from cloud must be passed as self._cloud_data_key
        self.untrack = True
        self.add({self._cloud_data_key: attachments})
        self.untrack = False

        # TODO: when it's a item attachment the attachment itself
        # is not downloaded. We must download it...
        # TODO: idea: retrieve the attachments ids' only with
        # select and then download one by one.
        return True