config sample generator cannot recognize DictOpt type options

Class DictOpt is defined in oslo.config.cfg
If we register a DictOpt type config option in nova, then the following error will be given when running tools/config/generate_sample.sh to generate nova.conf.sample:

'NoneType' object has no attribute 'group'

The tools/config/generate_sample.sh calls openstack.common.config.generator to execute the generation of config sample, and in openstack.common.config.generator there doesn't exist a way to process DictOpt type options:

STROPT = "StrOpt"
BOOLOPT = "BoolOpt"
INTOPT = "IntOpt"
FLOATOPT = "FloatOpt"
LISTOPT = "ListOpt"
MULTISTROPT = "MultiStrOpt"

OPT_TYPES = {
    STROPT: 'string value',
    BOOLOPT: 'boolean value',
    INTOPT: 'integer value',
    FLOATOPT: 'floating point value',
    LISTOPT: 'list value',
    MULTISTROPT: 'multi valued',
}

OPTION_REGEX = re.compile(r"(%s)" % "|".join([STROPT, BOOLOPT, INTOPT,
                                              FLOATOPT, LISTOPT,
                                              MULTISTROPT]))

…

def _print_opt(opt):
    opt_name, opt_default, opt_help = opt.dest, opt.default, opt.help
    if not opt_help:
        sys.stderr.write('WARNING: "%s" is missing help string.\n' % opt_name)
        opt_help = ""
    opt_type = None
    try:
        opt_type = OPTION_REGEX.search(str(type(opt))).group(0)
    except (ValueError, AttributeError) as err:
        sys.stderr.write("%s\n" % str(err))
        sys.exit(1)
    opt_help += ' (' + OPT_TYPES[opt_type] + ')'
    print('#', "\n# ".join(textwrap.wrap(opt_help, WORDWRAP_WIDTH)))
    if opt.deprecated_opts:
        for deprecated_opt in opt.deprecated_opts:
            if deprecated_opt.name:
                deprecated_group = (deprecated_opt.group if
                                    deprecated_opt.group else "DEFAULT")
                print('# Deprecated group/name - [%s]/%s' %
                      (deprecated_group,
                       deprecated_opt.name))
    try:
        if opt_default is None:
            print('#%s=<None>' % opt_name)
        elif opt_type == STROPT:
            assert(isinstance(opt_default, six.string_types))
            print('#%s=%s' % (opt_name, _sanitize_default(opt_name,
                                                          opt_default)))
        elif opt_type == BOOLOPT:
            assert(isinstance(opt_default, bool))
            print('#%s=%s' % (opt_name, str(opt_default).lower()))
        elif opt_type == INTOPT:
            assert(isinstance(opt_default, int) and
                   not isinstance(opt_default, bool))
            print('#%s=%s' % (opt_name, opt_default))
        elif opt_type == FLOATOPT:
            assert(isinstance(opt_default, float))
            print('#%s=%s' % (opt_name, opt_default))
        elif opt_type == LISTOPT:
            assert(isinstance(opt_default, list))
            print('#%s=%s' % (opt_name, ','.join(opt_default)))
        elif opt_type == MULTISTROPT:
            assert(isinstance(opt_default, list))
            if not opt_default:
                opt_default = ['']
            for default in opt_default:
                print('#%s=%s' % (opt_name, default))
        print('')
    except Exception:
        sys.stderr.write('Error in option "%s"\n' % opt_name)
        sys.exit(1)

Since the DictOpt value is not recognized , the code exits with an exception.
This problem will also affect tools/config/check_uptodate.sh because that also depend on the same module to process config sample generation.