Create a temporary container from a given iid.

        Temporary containers are marked with a sentinel environment
        variable so that they can be cleaned on unmount.

def _create_temp_container(self, iid):
        """
        Create a temporary container from a given iid.

        Temporary containers are marked with a sentinel environment
        variable so that they can be cleaned on unmount.
        """
        try:
            return self.client.create_container(
                image=iid, command='/bin/true',
                environment=['_ATOMIC_TEMP_CONTAINER'],
                detach=True, network_disabled=True)['Id']
        except docker.errors.APIError as ex:
            raise MountError('Error creating temporary container:\n%s' % str(ex))