run_tests on stable/icehouse is failing with AttributeError: can't set attribute

[Doug Fish]

On a fresh clone of Horizon stable/icehouse on an Ubuntu 12.04 machine there are 870 errors using run_tests.sh. The tests seem to fail similar to this:

======================================================================
ERROR: test_reject_random_string (openstack_dashboard.test.tests.utils.UtilsFilterTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/drf/stuff/icehouse/horizon/openstack_dashboard/test/helpers.py", line 124, in setUp
    test_utils.load_test_data(self)
  File "/home/drf/stuff/icehouse/horizon/openstack_dashboard/test/test_data/utils.py", line 43, in load_test_data
    data_func(load_onto)
  File "/home/drf/stuff/icehouse/horizon/openstack_dashboard/test/test_data/exceptions.py", line 60, in data
    TEST.exceptions.nova_unauthorized = create_stubbed_exception(nova_unauth)
  File "/home/drf/stuff/icehouse/horizon/openstack_dashboard/test/test_data/exceptions.py", line 44, in create_stubbed_exception
    return cls(status_code, msg)
  File "/home/drf/stuff/icehouse/horizon/openstack_dashboard/test/test_data/exceptions.py", line 31, in fake_init_exception
    self.code = code
AttributeError: can't set attribute