ValueError: number of bits must be greater than zero

Using the build from ppa:maas/proposed, we're seeing this error in regiond.log:

2017-07-18 18:25:43 maasserver.utils.views: [error] 500 Internal Server Error @ /MAAS/rpc/
Traceback (most recent call last):
  File "/usr/lib/python3.5/random.py", line 253, in choice
    i = self._randbelow(len(seq))
  File "/usr/lib/python3.5/random.py", line 230, in _randbelow
    r = getrandbits(k) # 0 <= r < 2**k
ValueError: number of bits must be greater than zero

This is resulting in MAAS returning 500 errors for all calls to the region controller.

2.2.2-6092-g9031a90-0ubuntu1~16.04.1