diff -r 3d4e9c994f10 -r a86126ab1dd4 wp/wp-includes/customize/class-wp-customize-new-menu-section.php
--- a/wp/wp-includes/customize/class-wp-customize-new-menu-section.php	Tue Oct 22 16:11:46 2019 +0200
+++ b/wp/wp-includes/customize/class-wp-customize-new-menu-section.php	Tue Dec 15 13:49:49 2020 +0100
@@ -8,6 +8,8 @@
  * @deprecated 4.9.0 This file is no longer used as of the menu creation UX introduced in #40104.
  */
 
+_deprecated_file( basename( __FILE__ ), '4.9.0' );
+
 /**
  * Customize Menu Section Class
  *
@@ -32,13 +34,14 @@
 	 * Any supplied $args override class property defaults.
 	 *
 	 * @since 4.9.0
+	 * @deprecated 4.9.0
 	 *
 	 * @param WP_Customize_Manager $manager Customizer bootstrap instance.
-	 * @param string               $id      An specific ID of the section.
+	 * @param string               $id      A specific ID of the section.
 	 * @param array                $args    Section arguments.
 	 */
 	public function __construct( WP_Customize_Manager $manager, $id, array $args = array() ) {
-		_deprecated_file( basename( __FILE__ ), '4.9.0' ); // @todo Move this outside of class, and remove its require_once() from class-wp-customize-section.php. See #42364.
+		_deprecated_function( __METHOD__, '4.9.0' );
 		parent::__construct( $manager, $id, $args );
 	}
 
@@ -46,8 +49,10 @@
 	 * Render the section, and the controls that have been added to it.
 	 *
 	 * @since 4.3.0
+	 * @deprecated 4.9.0
 	 */
 	protected function render() {
+		_deprecated_function( __METHOD__, '4.9.0' );
 		?>
 		<li id="accordion-section-<?php echo esc_attr( $this->id ); ?>" class="accordion-section-new-menu">
 			<button type="button" class="button add-new-menu-item add-menu-toggle" aria-expanded="false">