'This checker factory expects to get a list of
username:password pairs, with each pair also separated by a
colon. For example, the string \'alice:f:bob:g\' would generate
two users, one named \'alice\' and one named \'bob\'.'

def generateChecker(self, argstring):

    checker = InMemoryUsernamePasswordDatabaseDontUse()
    if argstring:
        pieces = argstring.split(':')
        if (len(pieces) % 2):
            from twisted.cred.strcred import InvalidAuthArgumentString
            raise InvalidAuthArgumentString('argstring    must    be    in    format    U:P:...')
        for i in range(0, len(pieces), 2):
            (username, password) = (pieces[i], pieces[(i + 1)])
            checker.addUser(username, password)
    return checker
