Comment 1 for bug 788265

In version:
2011.3-dev (2011.3-workspace:tarmac-20110602174653-azonyll6ctjjtxvf)

Commenting the "request_spec" argument makes it work:
     rpc.cast(context,
                     FLAGS.scheduler_topic,
                     {"method": "run_instance",
                      "args": {"topic": FLAGS.compute_topic,
                               "instance_id": instance_id,
                               #"request_spec": {
                               # 'instance_type': instance_type,
                               # 'filter':
                               # 'nova.scheduler.host_filter.'
                               # 'InstanceTypeFilter',
                               #},
                               "availability_zone": availability_zone,
                               "injected_files": injected_files,
                               "admin_password": admin_password,
                              },
                     })

See link for a possible explanation of the exception:
http://stackoverflow.com/questions/455580/json-datetime-between-python-and-javascript/2680060#2680060