'Supply a supplied credentials checker to the Options class.'

def addChecker(self, checker):

    supported = []
    if (self.supportedInterfaces is None):
        supported = checker.credentialInterfaces
    else:
        for interface in checker.credentialInterfaces:
            if self.supportsInterface(interface):
                supported.append(interface)
    if (not supported):
        raise UnsupportedInterfaces(checker.credentialInterfaces)
    if ('credInterfaces' not in self):
        self['credInterfaces'] = {}
    if ('credCheckers' not in self):
        self['credCheckers'] = []
    self['credCheckers'].append(checker)
    for interface in supported:
        self['credInterfaces'].setdefault(interface, []).append(checker)
