Update to Drupal 8.1.0. For more information, see https://www.drupal.org/drupal-8.1.0-release-notes

core/lib/Drupal/Component/FileSystem/RegexDirectoryIterator.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace Drupal\Component\FileSystem;
+
+/**
+ * Iterates over files whose names match a regular expression in a directory.
+ */
+class RegexDirectoryIterator extends \FilterIterator {
+
+  /**
+   * The regular expression to match.
+   *
+   * @var string
+   */
+  protected $regex;
+
+  /**
+   * RegexDirectoryIterator constructor.
+   *
+   * @param string $path
+   *   The path to scan.
+   * @param string $regex
+   *   The regular expression to match, including delimiters. For example,
+   *   /\.yml$/ would list only files ending in .yml.
+   */
+  public function __construct($path, $regex) {
+    // Use FilesystemIterator to not iterate over the the . and .. directories.
+    $iterator = new \FilesystemIterator($path);
+    parent::__construct($iterator);
+    $this->regex = $regex;
+  }
+
+  /**
+   * Implements \FilterIterator::accept().
+   */
+  public function accept() {
+    /** @var \SplFileInfo $file_info */
+    $file_info = $this->getInnerIterator()->current();
+    return $file_info->isFile() && preg_match($this->regex, $file_info->getFilename());
+  }
+
+}