bot_update: Use 'gclient' from same repository.

git_cache.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.
 
 """A git command for managing a local cache of git repositories."""
 
 from __future__ import print_function
 import errno
 import logging
@@ skipping 421 matching lines @@
       self._fetch(rundir, verbose, depth)
     except ClobberNeeded:
       # This is a major failure, we need to clean and force a bootstrap.
       gclient_utils.rmtree(rundir)
       self.print(GIT_CACHE_CORRUPT_MESSAGE)
       tempdir = self._ensure_bootstrapped(depth, bootstrap, force=True)
       assert tempdir
       self._fetch(tempdir or self.mirror_path, verbose, depth)
     finally:
       if tempdir:
-        try:
-          if os.path.exists(self.mirror_path):
-            gclient_utils.rmtree(self.mirror_path)
-          os.rename(tempdir, self.mirror_path)
-        except OSError as e:
-          # This is somehow racy on Windows.
-          # Catching OSError because WindowsError isn't portable and
-          # pylint complains.
-          self.print('Error moving %s to %s: %s' % (tempdir, self.mirror_path,
-                                                    str(e)))
+        if os.path.exists(self.mirror_path):
+          gclient_utils.rmtree(self.mirror_path)
+        os.rename(tempdir, self.mirror_path)
       if not ignore_lock:
         lockfile.unlock()
 
   def update_bootstrap(self, prune=False):
     # The files are named <git number>.zip
     gen_number = subprocess.check_output(
         [self.git_exe, 'number', 'master'], cwd=self.mirror_path).strip()
     # Run Garbage Collect to compress packfile.
     self.RunGit(['gc', '--prune=all'])
     # Creating a temp file and then deleting it ensures we can use this name.
@@ skipping 267 matching lines @@
   dispatcher = subcommand.CommandDispatcher(__name__)
   return dispatcher.execute(OptionParser(), argv)
 
 
 if __name__ == '__main__':
   try:
     sys.exit(main(sys.argv[1:]))
   except KeyboardInterrupt:
     sys.stderr.write('interrupted\n')
     sys.exit(1)