#2503 make singletons compared with "is" not == or !=
Thanks to Wummel for the patch
diff --git a/Lib/bsddb/dbshelve.py b/Lib/bsddb/dbshelve.py
index f5f8b9a..96f604a 100644
--- a/Lib/bsddb/dbshelve.py
+++ b/Lib/bsddb/dbshelve.py
@@ -133,7 +133,7 @@
 
 
     def keys(self, txn=None):
-        if txn != None:
+        if txn is not None:
             return self.db.keys(txn)
         else:
             return self.db.keys()
@@ -157,7 +157,7 @@
 
 
     def items(self, txn=None):
-        if txn != None:
+        if txn is not None:
             items = self.db.items(txn)
         else:
             items = self.db.items()
@@ -168,7 +168,7 @@
         return newitems
 
     def values(self, txn=None):
-        if txn != None:
+        if txn is not None:
             values = self.db.values(txn)
         else:
             values = self.db.values()
diff --git a/Lib/bsddb/test/test_basics.py b/Lib/bsddb/test/test_basics.py
index de935f7..9b38d57 100644
--- a/Lib/bsddb/test/test_basics.py
+++ b/Lib/bsddb/test/test_basics.py
@@ -363,7 +363,7 @@
         else:
             if set_raises_error:
                 self.fail("expected exception")
-            if n != None:
+            if n is not None:
                 self.fail("expected None: %r" % (n,))
 
         rec = c.get_both('0404', self.makeData('0404'))
@@ -377,7 +377,7 @@
         else:
             if get_raises_error:
                 self.fail("expected exception")
-            if n != None:
+            if n is not None:
                 self.fail("expected None: %r" % (n,))
 
         if self.d.get_type() == db.DB_BTREE:
diff --git a/Lib/bsddb/test/test_dbtables.py b/Lib/bsddb/test/test_dbtables.py
index 46602ce..faddd11 100644
--- a/Lib/bsddb/test/test_dbtables.py
+++ b/Lib/bsddb/test/test_dbtables.py
@@ -323,7 +323,7 @@
         self.tdb.Insert(tabname, {'Type': 'Unknown', 'Access': '0'})
 
         def set_type(type):
-            if type == None:
+            if type is None:
                 return 'MP3'
             return type