Server fails to return a list of data claiming type mismatch

[Chris Johns]

Ladon functions which have a return type of an array of anything won't return data.

The following code:

class V1(object):
    """
    This service returns events between two times for a given trackable.
    """
    @ladonize(rtype=[ PORTABLE_STRING ])
    def getGroupNames(self):
        """
        Returns a list of group names.
        @rtype: List of group names.
        """
        cnn = db.get_connection()
        sql = "blah blah sql"
        params = {}
        groups = db.execute_fetchall(cnn, sql, params)
        ret = []
        for g in groups:
            ret += [g["group_description"]]
        return ret

Gets the following error:
WebFault: Server raised fault: 'Return-type mismatch in V1::getGroupNames: Expected [<type 'unicode'>] recieved <type 'list'>'

It sees a list as a response, but won't accept it claiming it's not a list. (Or alternatively, it's expecting a list of unicode, and is failing on a list of unicode)