Make Lockfile._remove_lockfile more robust on win32

Make Lockfile._remove_lockfile more robust on win32

Sometimes, removing lockfiles fails on windows, for obscure reasons.
Following advice from gclient_utils.rmtree, lock file removal has
been improved by using the builtin executable 'del' and retrying 3
times in case it fails.

BUG=

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=264557

[pgervais, 2014-04-17 00:17:04]

This is supposed to fix the flaky issues we're having with the WinGit builder.
https://build.chromium.org/p/chromium.git/buildslaves/vm402-m1

This code works, I tested it on vm402-m1, but I don't know if it actually fixes
the problem.

[Ryan Tseng, 2014-04-17 08:20:22]

https://codereview.chromium.org/240653002/diff/1/git_cache.py
File git_cache.py (right):

https://codereview.chromium.org/240653002/diff/1/git_cache.py#newcode77
git_cache.py:77: raise LockError('Failed to remove lock: %s' % lockfile)
I think you want to put this outside the for loop

[pgervais, 2014-04-17 16:38:08]

On 2014/04/17 08:20:22, Ryan T. wrote:
> https://codereview.chromium.org/240653002/diff/1/git_cache.py
> File git_cache.py (right):
> 
> https://codereview.chromium.org/240653002/diff/1/git_cache.py#newcode77
> git_cache.py:77: raise LockError('Failed to remove lock: %s' % lockfile)
> I think you want to put this outside the for loop

Fixed.

This code (with the indentation issue) has been running on vm402-m1 all night,
and it seems the problem has gone away.

[Ryan Tseng, 2014-04-17 16:56:29]

lgtm ship it!

[pgervais, 2014-04-17 17:02:45]

The CQ bit was checked by pgervais@chromium.org

[commit-bot: I haz the power, 2014-04-17 17:02:56]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/pgervais@chromium.org/240653002/20001

[commit-bot: I haz the power, 2014-04-17 17:05:01]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-04-17 17:05:02]

Presubmit check for 240653002-20001 failed and returned exit status 1.

Running presubmit commit checks ...
Checking out rietveld...
Running save-description-on-failure.sh
Running push-basic.sh
Running upstream.sh
Running submit-from-new-dir.sh
Running abandon.sh
Running submodule-merge-test.sh
Running upload-local-tracking-branch.sh
Running hooks.sh
Running post-dcommit-hook-test.sh
Running upload-stale.sh
Running patch.sh
Running basic.sh

** Presubmit ERRORS **
Missing LGTM from an OWNER for these files:
    depot_tools/git_cache.py

Presubmit checks took 123.3s to calculate.

[pgervais, 2014-04-17 17:06:05]

On 2014/04/17 17:05:02, I haz the power (commit-bot) wrote:
> Presubmit check for 240653002-20001 failed and returned exit status 1.
> 
> Running presubmit commit checks ...
> Checking out rietveld...
> Running save-description-on-failure.sh
> Running push-basic.sh
> Running upstream.sh
> Running submit-from-new-dir.sh
> Running abandon.sh
> Running submodule-merge-test.sh
> Running upload-local-tracking-branch.sh
> Running hooks.sh
> Running post-dcommit-hook-test.sh
> Running upload-stale.sh
> Running patch.sh
> Running basic.sh
> 
> ** Presubmit ERRORS **
> Missing LGTM from an OWNER for these files:
>     depot_tools/git_cache.py
> 
> Presubmit checks took 123.3s to calculate.

maruel, could you lgtm that?

[M-A Ruel, 2014-04-17 17:17:19]

lgtm

https://codereview.chromium.org/240653002/diff/20001/git_cache.py
File git_cache.py (right):

https://codereview.chromium.org/240653002/diff/20001/git_cache.py#newcode64
git_cache.py:64: """Delete the lockfile. Complains (implicitly) if it doesn't
exist.
Deletes :)

[pgervais, 2014-04-17 17:22:01]

On 2014/04/17 17:17:19, M-A Ruel wrote:
> lgtm
> 
> https://codereview.chromium.org/240653002/diff/20001/git_cache.py
> File git_cache.py (right):
> 
> https://codereview.chromium.org/240653002/diff/20001/git_cache.py#newcode64
> git_cache.py:64: """Delete the lockfile. Complains (implicitly) if it doesn't
> exist.
> Deletes :)

Thanks! 

And I do think 'delete' is correct in this context (this beats me, but I've
always seen verbs with no 's' for describing function behavior.) Maybe Ryan can
help us understand that?

[pgervais, 2014-04-17 17:22:06]

The CQ bit was checked by pgervais@chromium.org

[commit-bot: I haz the power, 2014-04-17 17:22:22]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/pgervais@chromium.org/240653002/20001

[commit-bot: I haz the power, 2014-04-17 17:24:16]

Change committed as 264557