Merge rev 30547 from Zope-2_8-branch.

Use ZODB 3.4b3.

Stop using deprecated txn_mgr= argument; use
transaction_manager= instead.  Stop "illegal" use of
Connection's private ._txn_mgr attribute; use the new
public .transaction_manager attribute instead.

lib/python/Products/ZODBMountPoint/Mount.py

@@ -209,7 +209,7 @@ class ConnectionPatches:
                 # collector #1350: ensure that the connection is unregistered
                 # from the transaction manager (XXX API method?)
                 if conn._synch:
-                    conn._txn_mgr.unregisterSynch(conn)
+                    conn.transaction_manager.unregisterSynch(conn)
 
                 # The mounted connection keeps a reference to
                 # its database, but nothing else.

lib/python/ZClasses/ZClass.txt

@@ -76,7 +76,7 @@ transaction manager so that we can use the second connection without
 creating a separate thread:
 
     >>> tm2 = transaction.TransactionManager()
-    >>> conn2 = some_database.open(txn_mgr=tm2)
+    >>> conn2 = some_database.open(transaction_manager=tm2)
     >>> app2 = conn2.root()['Application']
     >>> test2 = app2.Control_Panel.Products['test']
     >>> c2 = test2.C()

lib/python/ZClasses/_pmc.txt

@@ -78,7 +78,7 @@ without having to use threads.
 
     >>> import transaction
     >>> tm = transaction.TransactionManager()
-    >>> connection = some_database.open(txn_mgr=tm)
+    >>> connection = some_database.open(transaction_manager=tm)
     >>> connection.root()['C'] = C
     >>> tm.commit()
 
@@ -125,7 +125,7 @@ Then the class will return to it's prior state:
 We can open another connection and access the class there.
 
     >>> tm2 = transaction.TransactionManager()
-    >>> connection2 = some_database.open(txn_mgr=tm2)
+    >>> connection2 = some_database.open(transaction_manager=tm2)
 
     >>> C2 = connection2.root()['C']
     >>> c2 = C2('other')
@@ -245,8 +245,8 @@ connections to a variable first to prevent getting them from the
 connection pool:
 
     >>> old = connection, connection2
-    >>> connection = some_database.open(txn_mgr=tm)
-    >>> connection2 = some_database.open(txn_mgr=tm2)
+    >>> connection = some_database.open(transaction_manager=tm)
+    >>> connection2 = some_database.open(transaction_manager=tm2)
    
 Now, we can read the object: