Config error prevents GUI from loading

[jgosmann]

I managed to write a Python file which, when opened in the GUI, will produce a blank page with this exception:

  File "/home/jgosmann/.pyenv/versions/3.5.3/lib/python3.5/site-packages/nengo_gui/server.py", line 235, in do_GET
    self.http_GET()
  File "/home/jgosmann/.pyenv/versions/3.5.3/lib/python3.5/site-packages/nengo_gui/server.py", line 251, in http_GET
    response = getattr(self, command)()
  File "/home/jgosmann/.pyenv/versions/3.5.3/lib/python3.5/site-packages/nengo_gui/guibackend.py", line 92, in auth_checked
    return fn(inst)
  File "/home/jgosmann/.pyenv/versions/3.5.3/lib/python3.5/site-packages/nengo_gui/guibackend.py", line 191, in serve_main
    page = self.server.create_page(filename, reset_cfg=reset_cfg)
  File "/home/jgosmann/.pyenv/versions/3.5.3/lib/python3.5/site-packages/nengo_gui/guibackend.py", line 390, in create_page
    reset_cfg=reset_cfg)
  File "/home/jgosmann/.pyenv/versions/3.5.3/lib/python3.5/site-packages/nengo_gui/page.py", line 110, in __init__
    self.load()
  File "/home/jgosmann/.pyenv/versions/3.5.3/lib/python3.5/site-packages/nengo_gui/page.py", line 172, in load
    self.config = self.load_config()
  File "/home/jgosmann/.pyenv/versions/3.5.3/lib/python3.5/site-packages/nengo_gui/page.py", line 287, in load_config
    config[self.model].pos = (0, 0)
  File "/home/jgosmann/.pyenv/versions/3.5.3/lib/python3.5/site-packages/nengo/config.py", line 201, in __setattr__
    % (key, type(self._configures).__name__))
nengo.exceptions.ConfigError: Cannot configure the built-in parameter 'pos' on an instance of 'Network'. Please set the attribute directly on the object.

File:

import nengo
import nengo_spa as spa

from imem.modules import GatedMemory, SimilarityThreshold

d = 64

with spa.Network() as model:
    model.vocabs.get_or_create(d).populate('Inc.unitary()')
    
    model.current = GatedMemory(d)
    model.updated = GatedMemory(d)
    nengo.Connection(
        model.current.output, model.updated.input,
        transform=model.vocabs[d]['Inc'].get_convolution_matrix())
    nengo.Connection(model.updated.output, model.current.input)
    
    model.pos = spa.State(d)
    
    model.last_stim = spa.State(d, feedback=1.)
    model.sim_th = SimilarityThreshold(d)
    nengo.Connection(model.pos.output, model.sim_th.input_a)
    nengo.Connection(model.last_stim.output, model.sim_th.input_b)

[jgosmann]

Note that this happens on both master and with the basic nengo_spa support (#29).

[tbekolay]

I believe this occurs because of the line model.pos = spa.State(d), since pos is an attribute the Nengo GUI adds to objects; see #562 and issues linked there.