We can use subprocess.Popen(shell=True) only on windows

dart/tools/bots/bot_utils.py

 #!/usr/bin/env python
 #
 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 import hashlib
 import imp
 import os
 import subprocess
@@ skipping 168 matching lines @@
       }[utils.GuessOS()]
       env['AWS_CREDENTIAL_FILE'] = boto_config
       env['BOTO_CONFIG'] = boto_config
 
     if GSUtil.GSUTIL_IS_SHELL_SCRIPT:
       gsutil_command = [GSUtil.GSUTIL_PATH]
     else:
       gsutil_command = [sys.executable, GSUtil.GSUTIL_PATH]
 
     run(gsutil_command + gsutil_args, env=env,
-        shell=GSUtil.GSUTIL_IS_SHELL_SCRIPT)
+        shell=(GSUtil.GSUTIL_IS_SHELL_SCRIPT and sys.platform == 'win32'))
 
   def upload(self, local_path, remote_path, recursive=False, public=False):
     assert remote_path.startswith('gs://')
 
     args = ['cp']
     if public:
       args += ['-a', 'public-read']
     if recursive:
       args += ['-R']
     args += [local_path, remote_path]
@@ skipping 26 matching lines @@
   if not mangled_filename:
     mangled_filename = os.path.basename(filename)
 
   checksum = CalculateChecksum(filename)
   checksum_filename = '%s.md5sum' % filename
 
   with open(checksum_filename, 'w') as f:
     f.write('%s *%s' % (checksum, mangled_filename))
 
   return checksum_filename