Add missing gettext import for issue466

tryton/plugin.py

@@ -1,7 +1,11 @@
-#This file is part of Tryton.  The COPYRIGHT file at the top level of this repository contains the full copyright notices and license terms.
+#This file is part of Tryton.  The COPYRIGHT file at the top level of
+#this repository contains the full copyright notices and license terms.
 import common
 import os
 import imp
+import gettext
+
+_ = gettext.gettext
 
 PLUGINS_PATH = os.path.join(os.path.dirname(__file__), 'plugins')
 MODULES = []