Make tools/submit_try safer

tools/submit_try

 #!/usr/bin/python
 
 # Copyright (c) 2013 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.
 
 
 """
 submit_try: Submit a try request.
 
@@ skipping 268 matching lines @@
     print proc.communicate()[0]
   else:
     # Find depot_tools. This is needed to import git_cl and trychange.
     sys.path.append(FindDepotTools())
     import git_cl
     import trychange
 
     cmd = [GIT, 'diff', git_cl.Changelist().GetUpstreamBranch(),
            '--no-ext-diff']
     proc = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-    if proc.wait() != 0:
+    git_data = proc.communicate()
+    if git_data[0] is None:
       raise Exception('Failed to capture git diff!')
 
     temp_dir = tempfile.mkdtemp()
     try:
       diff_file = os.path.join(temp_dir, 'patch.diff')
       with open(diff_file, 'wb') as f:
-        f.write(proc.communicate()[0])
-  
+        f.write(git_data[0])
+        f.close()
+
       try_args = ['--use_svn',
                   '--svn_repo', GetTryRepo(),
                   '--root', GetCheckoutRoot(is_svn),
                   '--bot', botlist,
                   '--diff', diff_file,
                   ]
       if args.revision:
         try_args.extend(['-r', args.revision])
 
       # Submit the try request.
@@ skipping 12 matching lines @@
   # Parse and validate the command-line arguments.
   args = ValidateArgs(sys.argv[1:], trybots=trybots, cq_trybots=cq_trybots,
                       is_svn=is_svn)
 
   # Submit the try request.
   SubmitTryRequest(args, is_svn=is_svn)
 
 
 if __name__ == '__main__':
   sys.exit(main())