Add users to 'banned', 'contributor', or 'moderator'.

def add_users(self, category):
        """Add users to 'banned', 'contributor', or 'moderator'."""
        mapping = {'banned': 'ban', 'contributor': 'make_contributor',
                   'moderator': 'make_moderator'}

        if category not in mapping:
            print('{!r} is not a valid option for --add'.format(category))
            return
        func = getattr(self.sub, mapping[category])
        print('Enter user names (any separation should suffice):')
        data = sys.stdin.read().strip()
        for name in re.split('[^A-Za-z0-9_]+', data):
            func(name)
            print('Added {!r} to {}'.format(name, category))