Merge branch '3.4' into 4.1

* 3.4:
  Use the real image URL for the filesystem tests
  [Finder] Update PHPdoc append()
  [DI] Fix phpdoc
  Fix code examples in PHPDoc
  [HttpKernel] Fix inheritdocs
  bumped Symfony version to 3.4.16
  updated VERSION for 3.4.15
  updated CHANGELOG for 3.4.15

Author: sroze

Catalogue/AbstractOperation.php

@@ -39,21 +39,20 @@ abstract class AbstractOperation implements OperationInterface
      * This array stores 'all', 'new' and 'obsolete' messages for all valid domains.
      *
      * The data structure of this array is as follows:
-     * ```php
-     * array(
-     *     'domain 1' => array(
-     *         'all' => array(...),
-     *         'new' => array(...),
-     *         'obsolete' => array(...)
-     *     ),
-     *     'domain 2' => array(
-     *         'all' => array(...),
-     *         'new' => array(...),
-     *         'obsolete' => array(...)
-     *     ),
-     *     ...
-     * )
-     * ```
+     *
+     *     array(
+     *         'domain 1' => array(
+     *             'all' => array(...),
+     *             'new' => array(...),
+     *             'obsolete' => array(...)
+     *         ),
+     *         'domain 2' => array(
+     *             'all' => array(...),
+     *             'new' => array(...),
+     *             'obsolete' => array(...)
+     *         ),
+     *         ...
+     *     )
      *
      * @var array The array that stores 'all', 'new' and 'obsolete' messages
      */