Postgres 8.4 not support json ('NoneType' object has no attribute 'cursor')

[avelino]

'NoneType' object has no attribute 'cursor'

/lib/python2.7/site-packages/opps/db/models/fields/jsonf.py in db_type
                return self.default()
            return copy.deepcopy(self.default)
        # If the field doesn't have a default, then we punt to models.Field.
        return super(JSONFieldBase, self).get_default()
    def db_type(self, connection):
        if connection.vendor == 'postgresql' and\
           connection.pg_version >= 90400: ...
            return 'json'