Introduce splaytree.KeyNotFoundError and use it for reporting...

tools/splaytree.py

 # Copyright 2008 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 18 matching lines @@
 class Node(object):
   """Nodes in the splay tree."""
 
   def __init__(self, key, value):
     self.key = key
     self.value = value
     self.left = None
     self.right = None
 
 
+class KeyNotFoundError(Exception):
+  """KeyNotFoundError is raised when removing a non-existing node."""
+
+  def __init__(self, key):
+    self.key = key
+
+
 class SplayTree(object):
   """The splay tree itself is just a reference to the root of the tree."""
 
   def __init__(self):
     """Create a new SplayTree."""
     self.root = None
 
   def IsEmpty(self):
     """Is the SplayTree empty?"""
     return not self.root
@@ skipping 19 matching lines @@
     else:
       node.right = self.root
       node.left = self.root.left
       self.root.left = None
     self.root = node
 
   def Remove(self, key):
     """Remove the node with the given key from the SplayTree."""
     # Raise exception for key that is not found if the tree is empty.
     if self.IsEmpty():
-      raise Exception('KeyNotFound')
+      raise KeyNotFoundError(key)
     # Splay on the key to move the node with the given key to the top.
     self.Splay(key)
     # Raise exception for key that is not found.
     if self.root.key != key:
-      raise Exception('KeyNotFound')
+      raise KeyNotFoundError(key)
     removed = self.root
     # Link out the root node.
     if not self.root.left:
       # No left child, so the new tree is just the right child.
       self.root = self.root.right
     else:
       # Left child exists.
       right = self.root.right
       # Make the original left child the new root.
       self.root = self.root.left
@@ skipping 116 matching lines @@
         left = current
         current = current.right
       else:
         break
     # Assemble.
     left.right = current.left
     right.left = current.right
     current.left = dummy.right
     current.right = dummy.left
     self.root = current