[2.1.1, trunk, bzr5510] Can't enlist machines

Oct 26 13:11:57 maas-enlisting-node cloud-init[1292]: + maas-ipmi-autodetect-tool
Oct 26 13:11:57 maas-enlisting-node cloud-init[1292]: + power_type=
Oct 26 13:11:57 maas-enlisting-node cloud-init[1292]: + maas-enlist --serverurl http://192.168.122.1:5240/MAAS/api/2.0/machines/
Oct 26 13:11:57 maas-enlisting-node cloud-init[1292]: % Total % Received % Xferd Average Speed Time Time Time Current
Oct 26 13:11:57 maas-enlisting-node cloud-init[1292]: Dload Upload Total Spent Left Speed
Oct 26 13:11:58 maas-enlisting-node cloud-init[1292]: #015 0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0#015100 166 0 0 100 166 0 470 --:--:-- --:--:-- --:--:-- 471
Oct 26 13:11:58 maas-enlisting-node cloud-init[1292]: curl: (22) The requested URL returned error: 400 BAD REQUEST
Oct 26 13:11:58 maas-enlisting-node cloud-init[1292]: + maas-enlist --serverurl http://192.168.122.1:5240/MAAS/api/2.0/machines/
Oct 26 13:11:58 maas-enlisting-node cloud-init[1292]: % Total % Received % Xferd Average Speed Time Time Time Current
Oct 26 13:11:58 maas-enlisting-node cloud-init[1292]: Dload Upload Total Spent Left Speed
Oct 26 13:11:58 maas-enlisting-node cloud-init[1292]: #015 0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0#015100 166 0 0 100 166 0 599 --:--:-- --:--:-- --:--:-- 601
Oct 26 13:11:58 maas-enlisting-node cloud-init[1292]: curl: (22) The requested URL returned error: 400 BAD REQUEST

==========================================================================

2016-10-26 09:34:32 [twisted.python.log#info] ::ffff:192.168.122.190 - - [26/Oct/2016:13:34:31 +0000] "POST /MAAS/api/2.0/machines/ HTTP/1.1" 400 37 "-" "curl/7.47.0"
2016-10-26 09:34:32 [maasserver#error] ################################ Exception: ['Failed to parse JSON power_parameters'] ################################
2016-10-26 09:34:32 [maasserver#error] Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/maasserver/forms.py", line 254, in _get_power_parameters
    power_parameters = json.loads(power_parameters)
  File "/usr/lib/python3.5/json/__init__.py", line 319, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python3.5/json/decoder.py", line 339, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python3.5/json/decoder.py", line 357, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/django/core/handlers/base.py", line 132, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/lib/python3/dist-packages/maasserver/utils/views.py", line 177, in view_atomic_with_post_commit_savepoint
    return view_atomic(*args, **kwargs)
  File "/usr/lib/python3.5/contextlib.py", line 30, in inner
    return func(*args, **kwds)
  File "/usr/lib/python3/dist-packages/maasserver/api/support.py", line 55, in __call__
    response = upcall(request, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/django/views/decorators/vary.py", line 21, in inner_func
    response = func(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/piston3/resource.py", line 190, in __call__
    result = self.error_handler(e, request, meth, em_format)
  File "/usr/lib/python3/dist-packages/piston3/resource.py", line 188, in __call__
    result = meth(request, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/maasserver/api/support.py", line 261, in dispatch
    return function(self, request, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/maasserver/api/machines.py", line 875, in create
    return create_machine(request)
  File "/usr/lib/python3/dist-packages/maasserver/api/machines.py", line 795, in create_machine
    form = Form(data=altered_query_data, request=request)
  File "/usr/lib/python3/dist-packages/maasserver/forms.py", line 223, in __init__
    WithPowerMixin.set_up_power_type(self, self.data)
  File "/usr/lib/python3/dist-packages/maasserver/forms.py", line 277, in set_up_power_type
    form, data, machine)
  File "/usr/lib/python3/dist-packages/maasserver/forms.py", line 256, in _get_power_parameters
    raise ValidationError("Failed to parse JSON power_parameters")
django.core.exceptions.ValidationError: ['Failed to parse JSON power_parameters']