Merge branch '4.4' into 5.1

* 4.4:
  [Filesystem] Check if failed unlink was caused by permission denied
  fix APCu installation for the nightly build job
  skip Vulcain-based tests if the binary cannot be executed

Filesystem.php

@@ -175,7 +175,7 @@ public function remove($files)
                 if (!self::box('rmdir', $file) && file_exists($file)) {
                     throw new IOException(sprintf('Failed to remove directory "%s": ', $file).self::$lastError);
                 }
-            } elseif (!self::box('unlink', $file) && file_exists($file)) {
+            } elseif (!self::box('unlink', $file) && (false !== strpos(self::$lastError, 'Permission denied') || file_exists($file))) {
                 throw new IOException(sprintf('Failed to remove file "%s": ', $file).self::$lastError);
             }
         }

Tests/FilesystemTest.php

@@ -11,6 +11,8 @@
 
 namespace Symfony\Component\Filesystem\Tests;
 
+use Symfony\Component\Filesystem\Exception\IOException;
+
 /**
  * Test class for Filesystem.
  */
@@ -334,6 +336,28 @@ public function testRemoveIgnoresNonExistingFiles()
         $this->assertFileDoesNotExist($basePath.'dir');
     }
 
+    public function testRemoveThrowsExceptionOnPermissionDenied()
+    {
+        $this->markAsSkippedIfChmodIsMissing();
+
+        $basePath = $this->workspace.\DIRECTORY_SEPARATOR.'dir_permissions';
+        mkdir($basePath);
+        $file = $basePath.\DIRECTORY_SEPARATOR.'file';
+        touch($file);
+        chmod($basePath, 0400);
+
+        try {
+            $this->filesystem->remove($file);
+            $this->fail('Filesystem::remove() should throw an exception');
+        } catch (IOException $e) {
+            $this->assertStringContainsString('Failed to remove file "'.$file.'"', $e->getMessage());
+            $this->assertStringContainsString('Permission denied', $e->getMessage());
+        } finally {
+            // Make sure we can clean up this file
+            chmod($basePath, 0777);
+        }
+    }
+
     public function testRemoveCleansInvalidLinks()
     {
         $this->markAsSkippedIfSymlinkIsMissing();