Add retries to file operations for Windows.

git_cache.py

Index: git_cache.py
diff --git a/git_cache.py b/git_cache.py
index 0f66de72e9746b170df01982ccbf6ebaf0ac1936..9054db8713a23ed111660be8dfaab8476da85ff1 100755
--- a/git_cache.py
+++ b/git_cache.py
@@ -181,7 +181,7 @@ class Mirror(object):
     else:
       self.print = print
 
-  def print_without_file(self, message, **kwargs):
+  def print_without_file(self, message, **_kwargs):
     self.print_func(message)
 
   @property
@@ -230,6 +230,26 @@ class Mirror(object):
         setattr(cls, 'cachepath', cachepath)
       return getattr(cls, 'cachepath')
 
+  def Rename(self, src, dst, count=3):
+    sleep_time = 1

[nodir, 2016/11/11 01:53:59]

Strange indentation 

+    while True:
+      try:
+        os.rename(src, dst)
+        return
+      except OSError as e:
+        # This is somehow racy on Windows.
+        # Catching OSError because WindowsError isn't portable and
+        # pylint complains.
+        if not count:
+          raise
+
+        self.print('Error moving [%s] to [%s] (%d retries remaining): %s' % (
+            src, dst, count, str(e)))

[nodir, 2016/11/11 01:53:59]

str unnecessary?

+        time.sleep(sleep_time)
+        count -= 1
+        sleep_time *= 2
+
+
   def RunGit(self, cmd, **kwargs):
     """Run git in a subprocess."""
     cwd = kwargs.setdefault('cwd', self.mirror_path)
@@ -441,7 +461,7 @@ class Mirror(object):
       if tempdir:
         if os.path.exists(self.mirror_path):
           gclient_utils.rmtree(self.mirror_path)
-        os.rename(tempdir, self.mirror_path)
+        self.Rename(tempdir, self.mirror_path)
       if not ignore_lock:
         lockfile.unlock()