Extensions Docs Server: Uniform handling of file not found errors

chrome/common/extensions/docs/server2/file_system.py

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import os
 
+class FileNotFoundError(Exception):
+  def __init__(self, filename):
+    Exception.__init__(self, filename)
+
 def _ProcessFileData(data, path):
   if os.path.splitext(path)[-1] not in ['.js', '.html', '.json']:
     return data
   try:
     return unicode(data, 'utf-8')
   except:
     return unicode(data, 'latin-1')
 
 class FileSystem(object):
   """A FileSystem interface that can read files and directories.
@@ skipping 18 matching lines @@
   def ReadSingle(self, path):
     """Reads a single file from the FileSystem.
     """
     return self.Read([path]).Get()[path]
 
   def Stat(self, path):
     """Gets the version number of |path| if it is a directory, or the parent
     directory if it is a file.
     """
     raise NotImplementedError()