Update the code to better reflect recommended style:

Use != instead of <> since <> is documented as "obsolescent".
Use "is" and "is not" when comparing with None or type objects.
diff --git a/Lib/pdb.py b/Lib/pdb.py
index db4a2cd..f4a0c89 100755
--- a/Lib/pdb.py
+++ b/Lib/pdb.py
@@ -553,7 +553,7 @@
 			first = max(1, self.curframe.f_lineno - 5)
 		else:
 			first = self.lineno + 1
-		if last == None:
+		if last is None:
 			last = first + 10
 		filename = self.curframe.f_code.co_filename
 		breaklist = self.get_file_breaks(filename)
@@ -895,7 +895,8 @@
 def post_mortem(t):
 	p = Pdb()
 	p.reset()
-	while t.tb_next <> None: t = t.tb_next
+	while t.tb_next is not None:
+		t = t.tb_next
 	p.interaction(t.tb_frame, t)
 
 def pm():