test: add DummyLocalizer.get_default_language.

product/ERP5Type/tests/utils.py

@@ -145,6 +145,9 @@ class DummyLocalizer:
   and erp5_content message catalogs. It's a list.
   """
   __allow_access_to_unprotected_subobjects__ = 1
+
+  _default_language = 'en'
+
   def __init__(self):
     self.erp5_ui = self.ui = DummyMessageCatalog()
     self.erp5_content = self.content = DummyMessageCatalog()
@@ -156,6 +159,9 @@ class DummyLocalizer:
       return getattr(self, key)
     raise KeyError, key
 
+  def get_default_language(self):
+    return self._default_language
+
   def get_selected_language(self):
     return self.lang