Merge branch '2.8' into 3.3

* 2.8:
  Revert "bug #24105 [Filesystem] check permissions if dump target dir is missing (xabbuh)"
  [Filesystem] skip tests if not applicable
  [Fabbot] Do not run php-cs-fixer if there are no change in src/
  [Security] Fix exception when use_referer option is true and referer is not set or empty
  Get KERNEL_DIR through $_ENV too for KernelTestCase
  check permissions if dump target dir is missing

Author: nicolas-grekas

Test/KernelTestCase.php

@@ -115,8 +115,8 @@ protected static function getKernelClass()
             return $class;
         }
 
-        if (isset($_SERVER['KERNEL_DIR'])) {
-            $dir = $_SERVER['KERNEL_DIR'];
+        if (isset($_SERVER['KERNEL_DIR']) || isset($_ENV['KERNEL_DIR'])) {
+            $dir = isset($_SERVER['KERNEL_DIR']) ? $_SERVER['KERNEL_DIR'] : $_ENV['KERNEL_DIR'];
 
             if (!is_dir($dir)) {
                 $phpUnitDir = static::getPhpUnitXmlDir();