Fix gclient hook for stubborn hooks.

gclient.py

 #!/usr/bin/env python
 # 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.
 
 """Meta checkout manager supporting both Subversion and GIT."""
 # Files
 #   .gclient      : Current client configuration, written by 'config' command.
 #                   Format is a Python script defining 'solutions', a list whose
 #                   entries each are maps binding the strings "name" and "url"
@@ skipping 1298 matching lines @@
     print(
 """
 WARNING: gclient detected an obsolete setting in your %s file.  The file has
 been automagically updated.  The previous version is available at %s.old.
 """ % (options.config_filename, options.config_filename))
 
     # Replace existing .gclient with the updated version.
     # Return a new GClient instance based on the new content.
     new_content = ast2str(a)
     dot_gclient_fn = os.path.join(path, options.config_filename)
-    os.rename(dot_gclient_fn, dot_gclient_fn + '.old')
-    fh = open(dot_gclient_fn, 'w')
-    fh.write(new_content)
-    fh.close()
+    try:
+      os.rename(dot_gclient_fn, dot_gclient_fn + '.old')
+    except OSError:
+      pass
+    with open(dot_gclient_fn, 'w') as fh:
+      fh.write(new_content)
     client = GClient(path, options)
     client.SetConfig(new_content)
     return client
 
   @staticmethod
   def LoadCurrentConfig(options):
     """Searches for and loads a .gclient file relative to the current working
     dir. Returns a GClient object."""
     if options.spec:
       client = GClient('.', options)
@@ skipping 857 matching lines @@
     print >> sys.stderr, 'Error: %s' % str(e)
     return 1
   finally:
     gclient_utils.PrintWarnings()
 
 
 if '__main__' == __name__:
   sys.exit(Main(sys.argv[1:]))
 
 # vim: ts=2:sw=2:tw=80:et: