'Migrates a running instance to a new machine.
:param server: instance id which comes from nova list.
:param host: destination host name.
:param block_migration: if True, do block_migration, can be set as
\'auto\'
:param force: forces to bypass the scheduler if host is provided.
:returns: An instance of novaclient.base.TupleWithMeta'

@api_versions.wraps('2.30')
def live_migrate(self, server, host, block_migration, force=None):

    body = {'host': host, 'block_migration': block_migration}
    if force:
        body['force'] = force
    return self._action('os-migrateLive', server, body)
