merged branch gimler/patch-3 (PR #5256)

Commits
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a7b4573 add format to exception message

Discussion
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add format to exception message

src/Symfony/Component/Translation/Writer/TranslationWriter.php

@@ -59,7 +59,7 @@ class TranslationWriter
     public function writeTranslations(MessageCatalogue $catalogue, $format, $options = array())
     {
         if (!isset($this->dumpers[$format])) {
-            throw new \InvalidArgumentException('There is no dumper associated with this format.');
+            throw new \InvalidArgumentException(sprintf('There is no dumper associated with format "%s".', $format));
         }
 
         // get the right dumper