py3: sortKey() must be a string as comparison between str and None/int/tuple now raises TypeError.

And Zope4 now mandates it to be a string ({Shared.DC.ZRDB.TM.TM,ITransactionManager}.sortKey()).

product/CMFActivity/ActivityBuffer.py

@@ -75,4 +75,4 @@ class ActivityBuffer(TM):
 
   def sortKey(self, *ignored):
     """Activities must be finished before databases commit transactions."""
-    return -1
+    return '-1'

product/CMFActivity/ActivityConnection.py

@@ -34,7 +34,7 @@ from Acquisition import aq_parent
 # If the sort order below doesn't work, we cannot guarantee the sort key
 # used below will actually result in the activity connection being committed
 # after the ZODB and Catalog data.
-assert None < 0 < '' < (), "Cannot guarantee commit of activities comes after the appropriate data"
+assert '\x00' < '-1' < '0' < '1' < '\xff', "Cannot guarantee commit of activities comes after the appropriate data"
 
 manage_addActivityConnectionForm = HTMLFile('dtml/connectionAdd', globals())
 
@@ -66,4 +66,4 @@ InitializeClass(ActivityConnection)
 
 class ActivityDB(DB):
 
-    _sort_key = (0,)
+    _sort_key = '\xff'

product/ERP5Type/TransactionalVariable.py

@@ -70,7 +70,7 @@ class TransactionalVariable(dict):
   _unregistered = True
 
   def sortKey(self):
-    return None
+    return '\x00'
 
   commit = tpc_vote = tpc_begin = tpc_abort = lambda self, transaction: None
 
@@ -128,7 +128,7 @@ class TransactionalResource(object):
     return not (args in tv or tv.add(args))
 
   def sortKey(self):
-    return 1
+    return '1'
 
   abort = commit = tpc_vote = tpc_begin = tpc_finish = tpc_abort = \
     lambda self, transaction: None