KnpU\OAuth2ClientBundle\Security\Exception\FinishRegistrationException::getMessageKey PHP Method

getMessageKey() public method

This method should *not* be called normally. The purpose of this exception is to be a "flag" for code that will redirect the user to some "finish registration" page. If this message is shown to your user, then you're missing this piece of your code.
public getMessageKey ( )
    public function getMessageKey()
    {
        return 'You need to finish registration to login.';
    }