Using files session handler, getting error for memcache

Just switched to php 7.1 and started getting an error:
   Message: session_start(): Cannot find save handler 'memcache' - session startup failed
   Filename: Session/Session.php 
   Line Number: 143

This happens when running the second line in the following, in _construct() of the controller:
        $this->load->database();
        $this->load->library(array('session','user_agent','form_validation'));

This is what I have in application/config/config.php:
    $config['sess_driver'] = 'database';

    $config['sess_save_path'] = 'ci_sessions';

    $config['sess_cookie_name'] = 'ih_sss';

    $config['sess_expiration'] = 1800;

    $config['sess_match_ip'] = FALSE;

    $config['sess_time_to_update'] = 300;
   $config['sess_regenerate_destroy'] = FALSE; 

Any help to try to sort this out would be much appreciated. 
Thanks.