/**
 * Show the Register link
 */
function videotube_login_form_bottom_register( $str, $args ){
    if( get_option( 'users_can_register' ) ){
        $str .= sprintf(
            '<p class="login-register"><a href="%s">%s</a></p>',
            esc_url( wp_registration_url() ),
            esc_html__( 'Register', 'videotube-child' )
        );
    }

    return $str;
}
add_filter( 'login_form_bottom', 'videotube_login_form_bottom_register', 10, 2 );