Copying a SPA model fails

[tcstewar]

Any model with nengo.spa doesn't seem to be able to be copied:

import nengo.spa as spa

model = spa.SPA()
with model:
    model.a = spa.Buffer(16)
m2 = model.copy()

AttributeError                            Traceback (most recent call last)
<ipython-input-8-4c0bfc568332> in <module>()
      4 with model:
      5     model.a = spa.Buffer(16)
----> 6 m2 = model.copy()

/home/tcstewar/github/nengo/nengo/network.pyc in copy(self, add_to_container)
    227             # However, we deal with it here, so we ignore the warning.
    228             warnings.simplefilter('ignore', category=NotAddedToNetworkWarning)
--> 229             c = deepcopy(self)
    230         if add_to_container is None:
    231             add_to_container = len(Network.context) > 0

/usr/lib/python2.7/copy.pyc in deepcopy(x, memo, _nil)
    188                             raise Error(
    189                                 "un(deep)copyable object of type %s" % cls)
--> 190                 y = _reconstruct(x, rv, 1, memo)
    191 
    192     memo[d] = y

/usr/lib/python2.7/copy.pyc in _reconstruct(x, info, deep, memo)
    334             state = deepcopy(state, memo)
    335         if hasattr(y, '__setstate__'):
--> 336             y.__setstate__(state)
    337         else:
    338             if isinstance(state, tuple) and len(state) == 2:

/home/tcstewar/github/nengo/nengo/network.pyc in __setstate__(self, state)
    206     def __setstate__(self, state):
    207         for k, v in iteritems(state):
--> 208             setattr(self, k, v)
    209         if len(Network.context) > 0:
    210             warnings.warn(NotAddedToNetworkWarning(self))

/home/tcstewar/github/nengo/nengo/spa/spa.pyc in __setattr__(self, key, value)
    108             if value.label is None:
    109                 value.label = key
--> 110             self._modules[key] = value
    111             for k, (obj, v) in iteritems(value.inputs):
    112                 if type(v) == int:

AttributeError: 'SPA' object has no attribute '_modules'