Added SafeRename to better handle problems with git processes locking directories.

gclient_utils.py

 # Copyright (c) 2012 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.
 
 """Generic utils."""
 
 import codecs
 import logging
 import os
 import pipes
@@ skipping 78 matching lines @@
       return s.decode('utf-8')
     except UnicodeDecodeError:
       return s
 
 
 def FileWrite(filename, content, mode='w'):
   with codecs.open(filename, mode=mode, encoding='utf-8') as f:
     f.write(content)
 
 
+def safe_rename(old, new):
+  """Renames a file reliably.
+
+  Sometimes os.rename does not work because a dying git process keeps a handle 
+  on it for a few seconds. An exception is then thrown, which make the program 
+  give up what it was doing and remove what was deleted.
+  The only solution is to catch the exception and try again until it works. 
+  """
+  # roughly 10s
+  retries = 100
+  for i in range(retries):
+    try:
+      os.rename(old, new)
+      break
+    except OSError:
+      if i == (retries - 1):
+        # Give up.
+        raise
+      # retry
+      logging.debug("Renaming failed from %s to %s. Retrying ..." % (old, new))
+      time.sleep(0.1)
+
+
 def rmtree(path):
   """shutil.rmtree() on steroids.
 
   Recursively removes a directory, even if it's marked read-only.
 
   shutil.rmtree() doesn't work on Windows if any of the files or directories
   are read-only, which svn repositories and some .svn files are.  We need to
   be able to force the files to be writable (i.e., deletable) as we traverse
   the tree.
 
@@ skipping 768 matching lines @@
 
   Python on OSX 10.6 raises a NotImplementedError exception.
   """
   try:
     import multiprocessing
     return multiprocessing.cpu_count()
   except:  # pylint: disable=W0702
     # Mac OS 10.6 only
     # pylint: disable=E1101
     return int(os.sysconf('SC_NPROCESSORS_ONLN'))