Update to Drupal 8.1.2. For more information, see https://www.drupal.org/project/drupal/releases/8.1.2

core/modules/book/book.module

@@ -127,7 +127,7 @@ function book_node_links_alter(array &$links, NodeInterface $node, array &$conte
 }
 
 /**
- * Implements hook_form_BASE_FORM_ID_alter() for node_form().
+ * Implements hook_form_BASE_FORM_ID_alter() for \Drupal\node\NodeForm.
  *
  * Adds the book form element to the node form.
  *
@@ -323,7 +323,7 @@ function book_node_prepare_form(NodeInterface $node, $operation, FormStateInterf
 }
 
 /**
- * Implements hook_form_BASE_FORM_ID_alter().
+ * Implements hook_form_BASE_FORM_ID_alter() for \Drupal\node\Form\NodeDeleteForm.
  *
  * Alters the confirm form for a single node deletion.
  */

core/modules/book/src/Access/BookNodeIsRemovableAccessCheck.php

@@ -10,7 +10,7 @@ use Drupal\node\NodeInterface;
 /**
  * Determines whether the requested node can be removed from its book.
  */
-class BookNodeIsRemovableAccessCheck implements AccessInterface{
+class BookNodeIsRemovableAccessCheck implements AccessInterface {
 
   /**
    * Book Manager Service.

core/modules/book/src/BookManager.php

@@ -720,7 +720,7 @@ class BookManager implements BookManagerInterface {
    * @param array $flat
    *   A flat array of the menu links from $tree, passed by reference.
    *
-   * @see static::bookTreeGetFlat().
+   * @see static::bookTreeGetFlat()
    */
   protected function flatBookTree(array $tree, array &$flat) {
     foreach ($tree as $data) {
@@ -1045,7 +1045,6 @@ class BookManager implements BookManagerInterface {
    *
    * @return array
    *   Book tree.
-   *
    */
   protected function buildBookOutlineRecursive(&$links, $parents, $depth) {
     $tree = array();

core/modules/book/src/BookManagerInterface.php

@@ -81,7 +81,6 @@ interface BookManagerInterface {
    *
    * @param int[] $nids
    *   An array of nids to load.
-   *
    * @param bool $translate
    *   If TRUE, set access, title, and other elements.
    *

core/modules/book/src/BookOutlineStorage.php

@@ -198,4 +198,5 @@ class BookOutlineStorage implements BookOutlineStorageInterface {
     }
     return $query->execute();
   }
+
 }

core/modules/book/src/BookOutlineStorageInterface.php

@@ -49,7 +49,6 @@ interface BookOutlineStorageInterface {
    *
    * @param array $book_link
    *   The book link.
-   *
    * @param int $max_depth
    *   The maximum supported depth of the book tree.
    *
@@ -166,4 +165,5 @@ interface BookOutlineStorageInterface {
    *   Array of unordered subtree book items.
    */
   public function getBookSubtree($link, $max_depth);
+
 }

core/modules/book/src/Controller/BookController.php

@@ -71,7 +71,6 @@ class BookController extends ControllerBase {
    *
    * @return array
    *   A render array representing the administrative page content.
-   *
    */
   public function adminOverview() {
     $rows = array();