Make ApplicationManger persistent again.

On first startup of a ZODB created with a Zope 2.13 instance, the Control_Panel should be deleted. To achieve this, we need to load it first, which breaks if the class is not persistent as before in Zope 2.13. This change can be removed in a future 5.0 as the Control_Panel is not present in ZODB in Zope 4.

CHANGES.rst

@@ -15,6 +15,8 @@ Bugs Fixed
 
 - Fix Content-Length header for non-ascii responses incl. a base tag.
 
+- Fix issue with ``Control_Panel`` on first startup of ZODB from Zope 2.13.
+
 
 Features Added
 ++++++++++++++

src/App/ApplicationManager.py

@@ -25,6 +25,7 @@
 from App.Undo import UndoSupport
 from App.version_txt import version_txt
 from OFS.Traversable import Traversable
+from Persistence import Persistent
 from Products.PageTemplates.PageTemplateFile import PageTemplateFile
 
 
@@ -80,7 +81,7 @@ def __bobo_traverse__(self, request, name):
 InitializeClass(DatabaseChooser)
 
 
-class ApplicationManager(Tabs, Traversable, Implicit):
+class ApplicationManager(Persistent, Tabs, Traversable, Implicit):
     """System management
     """
     __allow_access_to_unprotected_subobjects__ = 1