Update to Drupal 8.1.8. For more information, see https://www.drupal.org/project/drupal/releases/8.1.8

core/lib/Drupal/Core/StreamWrapper/LocalReadOnlyStream.php

@@ -15,6 +15,13 @@ namespace Drupal\Core\StreamWrapper;
  */
 abstract class LocalReadOnlyStream extends LocalStream {
 
+  /**
+   * {@inheritdoc}
+   */
+  public static function getType() {
+    return StreamWrapperInterface::READ_VISIBLE | StreamWrapperInterface::LOCAL;
+  }
+
   /**
    * Support for fopen(), file_get_contents(), etc.
    *