commit bc120b3c79bc40527df73d05d0f48137aaba37a2
Author: Erik Stielstra <info@erikstielstra.nl>
Date:   Tue Sep 17 13:31:53 2013 +0200

    #35

diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index 0b5d34d..2cbe4c2 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -2194,6 +2194,7 @@ function install_check_translations($install_state) {
   $files_directory = conf_path() . '/files';
   $translations_directory = conf_path() . '/files/translations';
   $translations_directory_exists = FALSE;
+  $translation_available = FALSE;
   $online = FALSE;
 
   // First attempt to create or make writable the files directory.
diff --git a/core/lib/Drupal/Core/StringTranslation/Translator/FileTranslation.php b/core/lib/Drupal/Core/StringTranslation/Translator/FileTranslation.php
index 42fd0c3..3e162b1 100644
--- a/core/lib/Drupal/Core/StringTranslation/Translator/FileTranslation.php
+++ b/core/lib/Drupal/Core/StringTranslation/Translator/FileTranslation.php
@@ -59,6 +59,10 @@ protected function loadLanguage($langcode) {
   /**
    * Finds installer translations either for a specific or all languages.
    *
+   * Filenames must match the pattern:
+   *  - 'drupal-[number].*.[langcode].po
+   *  - 'drupal-[number].*.*.po
+   *
    * @param string $langcode
    *   (optional) The language code corresponding to the language for which we
    *   want to find translation files. If omitted, information on all available
@@ -71,7 +75,7 @@ protected function loadLanguage($langcode) {
    * @see file_scan_directory()
    */
   public function findTranslationFiles($langcode = NULL) {
-    $files = file_scan_directory($this->directory, '!drupal-\d+\.\d+\.' . (!empty($langcode) ? preg_quote($langcode, '!') : '[^\.]+') . '\.po$!', array('recurse' => FALSE));
+    $files = file_scan_directory($this->directory, '!drupal-\d+\.[^\.]+\.' . (!empty($langcode) ? preg_quote($langcode, '!') : '[^\.]+') . '\.po$!', array('recurse' => FALSE));
     return $files;
   }