fix pylint warnings

native_client_sdk/src/build_tools/buildbot_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.
 
 """Common utilities for all buildbot scripts that specifically don't rely
 on having a full chromium checkout.
 """
 
 import os
 import subprocess
@@ skipping 44 matching lines @@
   interpretation of the arguments.  Shell behavior can differ between platforms
   so this should be avoided when not using platform dependent shell scripts."""
   print 'Running: ' + ' '.join(args)
   sys.stdout.flush()
   sys.stderr.flush()
   subprocess.check_call(args, cwd=cwd, env=env, shell=shell)
   sys.stdout.flush()
   sys.stderr.flush()
 
 
-def CopyDir(src, dst, excludes=['.svn', '*/.svn']):
+def CopyDir(src, dst, excludes=('.svn', '*/.svn')):
   """Recursively copy a directory using."""
   args = ['-r', src, dst]
   for exc in excludes:
     args.append('--exclude=' + exc)
   print 'cp -r %s %s' % (src, dst)
   if os.path.abspath(src) == os.path.abspath(dst):
     ErrorExit('ERROR: Copying directory onto itself: ' + src)
   oshelpers.Copy(args)
 
 
@@ skipping 46 matching lines @@
 
   subprocess.check_call(
       '%s cp -a public-read %s %s' % (GetGsutil(), filename, full_dst),
       shell=True,
       cwd=cwd)
   url = 'https://commondatastorage.googleapis.com/'\
         '%s/%s' % (bucket_path, filename)
   if step_link:
     print '@@@STEP_LINK@download@%s@@@' % url
     sys.stdout.flush()