TypeError: 'NoneType' object is not iterable in jujuclient.py

This bug shows up when we're running juju-core 1.22beta3, but not when we're running juju-core 1.21.1, with the same version of tools otherwise.

http://pastebin.ubuntu.com/10176461/

Stack trace:
2015-02-11 18:15:13,827 [ERROR] oil_ci.deploy.oil_deployer: Deployment failed: 'NoneType' object is not iterable
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/oil_ci/deploy/oil_deployer.py", line 140, in deploy
    debug=True, verbose=True)
  File "/usr/lib/python2.7/dist-packages/oil_ci/juju/juju_deployer.py", line 85, in run_deployer
    importer.Importer(env, deploy, options=opts).run()
  File "/usr/lib/python2.7/dist-packages/deployer/action/importer.py", line 196, in run
    self.deploy_services()
  File "/usr/lib/python2.7/dist-packages/deployer/action/importer.py", line 92, in deploy_services
    env_status = self.env.status()
  File "/usr/lib/python2.7/dist-packages/deployer/env/go.py", line 203, in status
    return self.client.get_stat()
  File "/usr/lib/python2.7/dist-packages/jujuclient.py", line 599, in get_stat
    return StatusTranslator().run(watch)
  File "/usr/lib/python2.7/dist-packages/jujuclient.py", line 999, in run
    self._unit(d)
  File "/usr/lib/python2.7/dist-packages/jujuclient.py", line 1031, in _unit
    for p in ports:

Versions:
ii juju-core 1.22-beta3-0ubuntu1~12.04.1~juju1
ii juju-deployer 0.4.3-0ubuntu1~ubuntu12.04.1~ppa1
ii python-jujuclient 0.18.4-5

This is on precise.