Call to undefined function user_external_login()

Is anyone else seeing this - or have I just gone insane?

Hi.

What other information do you need?

I certainly have oauth enabled! - 7.x-3.1

I have just downloaded the latest version (7.x-5.8) and this line of code exists:

from twitter/twitter_signin/twitter_signin.module

  if (isset($account->uid)) {
    user_external_login($account, $response);                    <--------------------- This guy!
    $success = TRUE;
  }

From all the reading I've done, user_external_login doesn't existing in Drupal 7 anymore. Indeed greping my entire Drupal tree, the only reference I find to this function is within the Twitter signin.module.

Is there a 3rd module I must install to get access to this function?

Please let me know what other information I can provide to assist with troubleshooting this.

Kind Regards,
Tim

Is there anything more I can do to help with this one?