Update vpython bootstrap to include Windows fix.

bootstrap/bootstrap_vpython.py

 #!/usr/bin/env python
 # Copyright 2017 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 import argparse
 import logging
 import os
 import subprocess
 import sys
 
 LOGGER = logging.getLogger(__name__)
 IS_WINDOWS = sys.platform == 'win32'
 EXE_EXTENSION = '.bat' if IS_WINDOWS else ''
 
 # /path/to/recipes-py
 ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 CIPD_ROOT = os.path.join(ROOT, '.cipd_root')
 
 VPYTHON_PACKAGE = 'infra/tools/luci/vpython/${platform}'
-VPYTHON_VERSION = 'git_revision:ea5f3c7c274276673049e6bc2fa2619b1f55d589'
+VPYTHON_VERSION = 'git_revision:4ff2211fe419a7a0083ea2010ea8b33fb5e342a9'
 
 
 def _ensure_vpython(cipd_root):
   manifest = '%s %s' % (VPYTHON_PACKAGE, VPYTHON_VERSION)
 
   cipd_bin = 'cipd' + EXE_EXTENSION
   cmd = [cipd_bin, 'ensure', '-root', cipd_root, '-ensure-file=-']
 
   LOGGER.debug('Running CIPD ensure command (cwd=%s): %s', os.getcwd(), cmd)
   proc = subprocess.Popen(
@@ skipping 56 matching lines @@
     return subprocess.call(vpython_args)
 
   vpython_args += ['--'] + opts.args
   LOGGER.debug('Executing bootstrapped Python: %s', vpython_args)
   return subprocess.call(vpython_args)
 
 
 if __name__ == '__main__':
   logging.basicConfig()
   sys.exit(main(sys.argv[1:]))