MAAS server gave an unexpected response: 503

It seems maas-deployer is too early to access API.

2016-03-15 09:52:52,996 INFO Waiting for cloud-init to complete - this usually takes several minutes
2016-03-15 09:58:11,957 INFO done.
2016-03-15 09:58:14,855 ERROR The MAAS server gave an unexpected response: 503

The MAAS server gave an unexpected response: 503

Traceback (most recent call last):
  File "/usr/bin/maas-deployer", line 9, in <module>
    load_entry_point('maas-deployer==0.0.6', 'console_scripts', 'maas-deployer')()
  File "/usr/lib/python2.7/dist-packages/maas_deployer/cli.py", line 88, in main
    engine.deploy(target)
  File "/usr/lib/python2.7/dist-packages/maas_deployer/vmaas/engine.py", line 71, in deploy
    ssh_user=maas_config['user'])
  File "/usr/lib/python2.7/dist-packages/maas_deployer/vmaas/maasclient/__init__.py", line 29, in __init__
    self.driver = self._get_driver(api_url, api_key, **kwargs)
  File "/usr/lib/python2.7/dist-packages/maas_deployer/vmaas/maasclient/__init__.py", line 33, in _get_driver
    return SSHDriver(api_url, api_key, ssh_user=kwargs['ssh_user'])
  File "/usr/lib/python2.7/dist-packages/maas_deployer/vmaas/maasclient/clidriver.py", line 338, in __init__
    self._login(api_url, api_key)
  File "/usr/lib/python2.7/dist-packages/maas_deployer/vmaas/maasclient/clidriver.py", line 355, in _login
    execc(cmd, stdin=self.cmd_stdin)
  File "/usr/lib/python2.7/dist-packages/maas_deployer/vmaas/util.py", line 111, in execc
    output=stderr)
subprocess.CalledProcessError: Command 'ssh -i /home/ubuntu/.ssh/id_maas -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -o LogLevel=quiet ubuntu@172.16.X.Y maas
login maas http://172.16.X.Y/MAAS/api/1.0 SECRET' returned non-zero exit status 1

[regiond.log]
2016-03-15 00:58:02 [-] Site starting on 5240
2016-03-15 00:58:02 [-] Factory starting on 5253
2016-03-15 00:58:14 [HTTPChannel,0,127.0.0.1] 127.0.0.1 - - [15/Mar/2016:00:58:14 +0000] "GET
/MAAS/api/1.0/nodegroups/?op=list HTTP/1.1" 503 164 "-" "Python-httplib2/0.8 (gzip)"
2016-03-15 01:02:18 [HTTPChannel,0,127.0.0.1] 127.0.0.1 - - [15/Mar/2016:01:02:18 +0000] "GET
/MAAS/rpc/ HTTP/1.1" 503 164 "-" "provisioningserver.rpc.clusterservice.ClusterClientService"
2016-03-15 01:02:18 [maas.websocket.listener] Listening for database notifications.
2016-03-15 01:02:18 [HTTPChannel,0,127.0.0.1] 127.0.0.1 - - [15/Mar/2016:01:02:17 +0000] "GET
/MAAS/rpc/ HTTP/1.1" 503 164 "-" "provisioningserver.rpc.clusterservice.ClusterClientService"
2016-03-15 01:02:18 [maas.websocket.listener] Listening for database notifications.
2016-03-15 01:02:18 [maas.websocket.listener] Listening for database notifications.
2016-03-15 01:02:18 [maas.websocket.listener] Listening for database notifications.
2016-03-15 01:02:19 [-] Cluster (master) did not import boot resources; it is not connected to
 the region at this time.
2016-03-15 01:02:20 [-] 127.0.0.1 - - [15/Mar/2016:01:02:20 +0000] "GET /MAAS/rpc/ HTTP/1.1" 2
00 472 "-" "provisioningserver.rpc.clusterservice.ClusterClientService"

[clusterd.log]
2016-03-15 00:58:10+0000 [-] Starting protocol <tftp.protocol.TFTP instance at 0x7f458b572ef0>
2016-03-15 00:58:10+0000 [-] TFTP Listener started at 127.0.0.1:69
2016-03-15 01:02:18+0000 [HTTPPageGetter,client] Region is not advertising RPC endpoints.
2016-03-15 01:02:18+0000 [HTTPPageGetter,client] Region is not advertising RPC endpoints.
2016-03-15 01:02:20+0000 [Uninitialized] ClusterClient connection established (HOST:IPv4Address(TCP, '127.0.0.1', 39922) PEER:IPv4Address(TCP, u'127.0.0.1', 5252))
2016-03-15 01:02:20+0000 [Uninitialized] ClusterClient connection established (HOST:IPv4Address(TCP, '192.168.70.23', 36915) PEER:IPv4Address(TCP, u'192.168.70.23', 5250))
2016-03-15 01:02:20+0000 [ClusterClient,client] Event-loop 'maas:pid=30556' authenticated.
2016-03-15 01:02:20+0000 [Uninitialized] ClusterClient connection established (HOST:IPv4Address(TCP, '127.0.0.1', 45240) PEER:IPv4Address(TCP, u'127.0.0.1', 5251))