Make bot_update on win more resilient

recipe_modules/bot_update/resources/bot_update.py

Index: recipe_modules/bot_update/resources/bot_update.py
diff --git a/recipe_modules/bot_update/resources/bot_update.py b/recipe_modules/bot_update/resources/bot_update.py
index 3211369667372e4ec45a6b52343120b69985a912..ea6ec9b9ceeeddcba973787b9dece31169d79b5a 100755
--- a/recipe_modules/bot_update/resources/bot_update.py
+++ b/recipe_modules/bot_update/resources/bot_update.py
@@ -518,6 +518,11 @@ def git_checkout(solutions, revisions, shallow, refs, git_cache_dir):
           refspec = '%s:%s' % (ref, ref.lstrip('+'))
           git('fetch', 'origin', refspec, cwd=sln_dir)
 
+        # Windows sometimes has trouble deleting files.
+        # This can make git commands that rely on locks fail.
+        if sys.platform.startswith('win'):
+          call('gclient.bat', 'cleanup', '--break_repo_locks')

[ddoman1, 2016/10/25 21:55:23]

I am afraid that it may be a better choice to copy & paste "def
_maybe_break_locks()" from gclient_scm.py to bot_update.py.

#1. CMDcleanup() has been marked as deprecated
:
https://chromium.googlesource.com/chromium/tools/depot_tools.git/+/master/gcl...

#2. invoking gclient within git_checkout() may fail.

From
https://chromium.googlesource.com/chromium/tools/depot_tools.git/+/master/rec...

" # Get a checkout of each solution, without DEPS or hooks.
  # Calling git directly because there is no way to run Gclient without
  # invoking DEPS."

[agable, 2016/10/28 16:55:34]

I'm the one deprecating cleanup (which has always previously been a no-op for
Git), so I told Katie to take this approach.
This is unfortunately a really good point. Nothing else in this git_checkouts
function invokes gclient, and that's probably on purpose. Dang.

[katthomas, 2016/10/28 23:40:29]

Done.

+
         revision = get_target_revision(name, url, revisions) or 'HEAD'
         force_revision(sln_dir, revision)
         done = True