Give dumbdbm a sync() method which Shelve can call.  Should solve some
database corruption problems with Spambayes.
diff --git a/Lib/dumbdbm.py b/Lib/dumbdbm.py
index 7b4ddb0..b85844d 100644
--- a/Lib/dumbdbm.py
+++ b/Lib/dumbdbm.py
@@ -110,6 +110,8 @@
             f.write("%r, %r\n" % (key, pos_and_siz_pair))
         f.close()
 
+    sync = _commit
+
     def __getitem__(self, key):
         pos, siz = self._index[key]     # may raise KeyError
         f = _open(self._datfile, 'rb')