Merge branch '4.4' into 5.2

* 4.4:
  [HttpKernel] do is_file check before include
  [PhpUnitBridge] fix reporting deprecations from DebugClassLoader
  [FrameworkBundle] skip deprecation in integration tests

Author: nicolas-grekas

Kernel.php

@@ -466,7 +466,7 @@ protected function initializeContainer()
                 if (!flock($lock, $wouldBlock ? \LOCK_SH : \LOCK_EX)) {
                     fclose($lock);
                     $lock = null;
-                } elseif (!\is_object($this->container = include $cachePath)) {
+                } elseif (!is_file($cachePath) || !\is_object($this->container = include $cachePath)) {
                     $this->container = null;
                 } elseif (!$oldContainer || \get_class($this->container) !== $oldContainer->name) {
                     flock($lock, \LOCK_UN);