Update to Drupal 8.2.0. For more information, see https://www.drupal.org/project/drupal/releases/8.2.0

core/lib/Drupal/Core/Authentication/AuthenticationCollectorInterface.php

@@ -41,7 +41,7 @@ interface AuthenticationCollectorInterface {
    * @param string $provider_id
    *   The provider ID.
    *
-   * @return \Drupal\Core\Authentication\AuthenticationProviderInterface|NULL
+   * @return \Drupal\Core\Authentication\AuthenticationProviderInterface|null
    *   The authentication provider which matches the ID.
    */
   public function getProvider($provider_id);

core/lib/Drupal/Core/Authentication/AuthenticationManager.php

@@ -94,7 +94,7 @@ class AuthenticationManager implements AuthenticationProviderInterface, Authenti
    * @param \Symfony\Component\HttpFoundation\Request $request
    *   The incoming request.
    *
-   * @return string|NULL
+   * @return string|null
    *   The id of the first authentication provider which applies to the request.
    *   If no application detects appropriate credentials, then NULL is returned.
    */
@@ -112,7 +112,7 @@ class AuthenticationManager implements AuthenticationProviderInterface, Authenti
    * @param \Symfony\Component\HttpFoundation\Request $request
    *   The incoming request.
    *
-   * @return string|NULL
+   * @return string|null
    *   The ID of the first authentication provider which applies to the request.
    *   If no application detects appropriate credentials, then NULL is returned.
    */

core/lib/Drupal/Core/Authentication/AuthenticationProviderChallengeInterface.php

@@ -21,7 +21,7 @@ interface AuthenticationProviderChallengeInterface {
    * @param \Exception $previous
    *   The previous exception.
    *
-   * @return \Symfony\Component\HttpKernel\Exception\HttpExceptionInterface|NULL
+   * @return \Symfony\Component\HttpKernel\Exception\HttpExceptionInterface|null
    *   An exception to be used in order to generate an authentication challenge.
    */
   public function challengeException(Request $request, \Exception $previous);

core/lib/Drupal/Core/Authentication/AuthenticationProviderInterface.php

@@ -24,10 +24,10 @@ interface AuthenticationProviderInterface {
   /**
    * Authenticates the user.
    *
-   * @param \Symfony\Component\HttpFoundation\Request|NULL $request
+   * @param \Symfony\Component\HttpFoundation\Request|null $request
    *   The request object.
    *
-   * @return \Drupal\Core\Session\AccountInterface|NULL
+   * @return \Drupal\Core\Session\AccountInterface|null
    *   AccountInterface - in case of a successful authentication.
    *   NULL - in case where authentication failed.
    */