Merge pull request django-cms#3363 from sthzg/patch-2

Updated docs

Author: digi604

docs/extending_cms/custom_plugins.rst

@@ -268,6 +268,14 @@ clause.
     field, as it is declared as a property of :class:`cms.models.pluginmodel.CMSPlugin`,
     and your plugin will not work as intended in the administration without
     further work.
+    
+.. warning::
+
+    If you are using Python 2.x and overriding the ``__unicode__`` method of the 
+    model file, make sure to return its results as UTF8-string. Otherwise 
+    saving an instance of your plugin might fail with the frontend editor showing 
+    an <Empty> plugin instance. To return in unicode use a return statement like
+    ``return u'{}'.format(self.guest_name)``.
 
 .. _handling-relations: