Not working for URL

I am trying to test
http://localhost:8000/mutillidae/webservices/rest/ws-user-account.php?username=adrian
I have used the following command
syntribos --config-file /root/syntribos/examples/configs/keystone.conf -t SQL_INJECTION_URL run

But this is not working. I tried to debug and and found:
1. It is not getting any task.
2. It is calling _fuzz_data() which is calling:
 model_iter = _build_dict_combinations(stri, data, skip_var)
For URL, it is getting null model_iter. It is happening because of the following:

def _build_str_combinations(fuzz_string, data):
    var_regex = r"{([\w]*):?([^}]*)}"
    for match in re.finditer(var_regex, data):
        start, stop = match.span()
        model = "{0}{1}{2}".format(data[:start], fuzz_string, data[stop:])
        if match.group(1):
            # The string is of the format "{identifier:value}", so we just
            # want the identifier as the param_path
            yield model, match.group(1)
        else:
            yield model, match.group(0)

As the for loop is not working for URL. So it is not getting anything and hence returning null.

Please see what can be done in this case.