Fix gsutil execution on Windows.

gsutil.py

 #!/usr/bin/env python
 # Copyright 2014 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.
 
 """Run a pinned gsutil."""
 
 
 import argparse
 import base64
@@ skipping 10 matching lines @@
 GSUTIL_URL = 'https://storage.googleapis.com/pub/'
 API_URL = 'https://www.googleapis.com/storage/v1/b/pub/o/'
 
 THIS_DIR = os.path.dirname(os.path.abspath(__file__))
 DEFAULT_BIN_DIR = os.path.join(THIS_DIR, 'external_bin', 'gsutil')
 DEFAULT_FALLBACK_GSUTIL = os.path.join(
     THIS_DIR, 'third_party', 'gsutil', 'gsutil')
 
 
 class SubprocessError(Exception):
-  pass
+  def __init__(self, message=None, code=0):
+    super(SubprocessError, self).__init__(message)
+    self.code = code
 
 
 class InvalidGsutilError(Exception):
   pass
 
 
 def call(args, verbose=True, **kwargs):
   kwargs['stdout'] = subprocess.PIPE
   kwargs['stderr'] = subprocess.STDOUT
   proc = subprocess.Popen(args, **kwargs)
   out = []
   for line in proc.stdout:
     out.append(line)
     if verbose:
       sys.stdout.write(line)
   code = proc.wait()
   if code:
-    raise SubprocessError('%s failed with %s' % (args, code))
+    raise SubprocessError('%s failed with %s' % (args, code), code)
   return ''.join(out)
 
 
 def download_gsutil(version, target_dir):
   """Downloads gsutil into the target_dir."""
   filename = 'gsutil_%s.zip' % version
   target_filename = os.path.join(target_dir, filename)
 
   # Check if the target exists already.
   if os.path.exists(target_filename):
@@ skipping 58 matching lines @@
 
   return gsutil_bin
 
 
 def run_gsutil(force_version, fallback, target, args):
   if force_version:
     gsutil_bin = ensure_gsutil(force_version, target)
   else:
     gsutil_bin = fallback
   cmd = [sys.executable, gsutil_bin] + args
-  os.execv(cmd[0], cmd)
+  try:
+    call(cmd)
+  except SubprocessError as e:
+    return e.code
+  return 0
 
 
 def parse_args():
   parser = argparse.ArgumentParser()
   parser.add_argument('--force-version')
   parser.add_argument('--fallback', default=DEFAULT_FALLBACK_GSUTIL)
   parser.add_argument('--target', default=DEFAULT_BIN_DIR)
   parser.add_argument('args', nargs=argparse.REMAINDER)
 
   args, extras = parser.parse_known_args()
   if args.args and args.args[0] == '--':
     args.args.pop(0)
   if extras:
     args.args = extras + args.args
   return args.force_version, args.fallback, args.target, args.args
 
 
 def main():
   force_version, fallback, target, args = parse_args()
-  run_gsutil(force_version, fallback, target, args)
+  return run_gsutil(force_version, fallback, target, args)
 
 if __name__ == '__main__':
   sys.exit(main())