add PRESUBMIT for native_client_sdk.

native_client_sdk/src/build_tools/sdk_tools/sdk_update_common.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.
 
+"""Utility functions for sdk_update.py and sdk_update_main.py."""
+
 import errno
 import os
 import shutil
 import subprocess
 import sys
 import time
 
-"""Utility functions for sdk_update.py and sdk_update_main.py."""
-
 
 class Error(Exception):
   """Generic error/exception for sdk_update module"""
   pass
 
 
 def RemoveDir(outdir):
   """Removes the given directory
 
   On Unix systems, this just runs shutil.rmtree, but on Windows, this doesn't
   work when the directory contains junctions (as does our SDK installer).
   Therefore, on Windows, it runs rmdir /S /Q as a shell command.  This always
   does the right thing on Windows. If the directory already didn't exist,
   RemoveDir will return successfully without taking any action.
 
   Args:
     outdir: The directory to delete
 
   Raises:
     CalledProcessError - if the delete operation fails on Windows
     OSError - if the delete operation fails on Linux
   """
 
   try:
     shutil.rmtree(outdir)
-  except:
+  except OSError:
     if not os.path.exists(outdir):
       return
     # On Windows this could be an issue with junctions, so try again with rmdir
     if sys.platform == 'win32':
       subprocess.check_call(['rmdir', '/S', '/Q', outdir], shell=True)
 
 
 def RenameDir(srcdir, destdir):
   """Renames srcdir to destdir. Removes destdir before doing the
      rename if it already exists."""
 
   max_tries = 5
+  num_tries = 0
   for num_tries in xrange(max_tries):
     try:
       RemoveDir(destdir)
       os.rename(srcdir, destdir)
       return
     except OSError as err:
       if err.errno != errno.EACCES:
         raise err
       # If we are here, we didn't exit due to raised exception, so we are
       # handling a Windows flaky access error.  Sleep one second and try
       # again.
       time.sleep(num_tries + 1)
+
   # end of while loop -- could not RenameDir
-  raise Error('Could not RenameDir %s => %s after %d tries.\n' %
+  raise Error('Could not RenameDir %s => %s after %d tries.\n'
               'Please check that no shells or applications '
               'are accessing files in %s.'
               % (srcdir, destdir, num_tries, destdir))