Merge branch '3.4' into 4.2

* 3.4:
  fix translating file validation error message
  [Validator] Add missing Hungarian translations
  [3.4] [Validator] Add missing french validation translations.
  [Validator] Only traverse arrays that are cascaded into
  Handle case where no translations were found
  [Validator] Translate unique collection message to Hungarian
  fix tests
  Run test in separate process
  Use a class name that does not actually exist
  fix horizontal spacing of inlined Bootstrap forms
  [Translator] Warm up the translations cache in dev
  turn failed file uploads into form errors

Resources/config/form.xml

@@ -70,6 +70,9 @@
             <tag name="form.type" />
             <argument type="service" id="form.choice_list_factory"/>
         </service>
+        <service id="form.type.file" class="Symfony\Component\Form\Extension\Core\Type\FileType" public="true">
+            <argument type="service" id="translator" on-invalid="ignore" />
+        </service>
 
         <service id="form.type_extension.form.transformation_failure_handling" class="Symfony\Component\Form\Extension\Core\Type\TransformationFailureExtension">
             <tag name="form.type_extension" extended-type="Symfony\Component\Form\Extension\Core\Type\FormType" />