Use the right display_format for Datetime

tryton/gui/window/view_form/view/list_gtk/parser.py

@@ -396,9 +396,9 @@ class Datetime(Date):
 
     def __init__(self, field_name, model, treeview=None, attrs=None,
             window=None):
-        self.display_format = date_format() + ' ' + HM_FORMAT
-        return super(Datetime, self).__init__(field_name, model,
+        super(Datetime, self).__init__(field_name, model,
                 treeview=treeview, attrs=attrs, window=window)
+        self.display_format = date_format() + ' ' + HM_FORMAT
 
     def get_textual_value(self, model):
         value = model[self.field_name].get_client(model)