Add warning batching in gclient_utils

Add warning batching in gclient_utils

BUG=

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=258982

[borenet, 2014-03-24 16:09:00]

Is this a sensible way to do this?  For context, see discussion on
https://codereview.chromium.org/195913002/.  In particular:

"""
As mentioned offline, it would be good to have a general facility to batch
warnings to the end of the command. Right now they get swallowed when they're
printed inline during the run.
"""

[M-A Ruel, 2014-03-24 16:25:30]

https://codereview.chromium.org/209393006/diff/1/gclient_utils.py
File gclient_utils.py (right):

https://codereview.chromium.org/209393006/diff/1/gclient_utils.py#newcode50
gclient_utils.py:50: atexit.register(_DisplayWarningsAtExit)
I'd prefer something more formal, a try/finally in the main loop instead of
relying on atexit.

[borenet, 2014-03-24 17:29:48]

Uploaded patch set 2, which changes to use try/except.  It makes sense to me to
do this in Main(), but it might also make sense to push it down into
GClient.RunOnDeps.

[M-A Ruel, 2014-03-24 17:53:06]

lgtm

https://codereview.chromium.org/209393006/diff/2/gclient_utils.py
File gclient_utils.py (right):

https://codereview.chromium.org/209393006/diff/2/gclient_utils.py#newcode43
gclient_utils.py:43: """Print any accumulated warnings."""
Prints

https://codereview.chromium.org/209393006/diff/2/gclient_utils.py#newcode51
gclient_utils.py:51: """Add the given warning message to the list of accumulated
warnings."""
Adds

https://codereview.chromium.org/209393006/diff/2/gclient_utils.py#newcode52
gclient_utils.py:52: _WARNINGS.append(msg)
In theory you'd need a lock. In practice, it's not a big deal.

[borenet, 2014-03-24 18:01:48]

Uploaded patch set 3.

https://codereview.chromium.org/209393006/diff/2/gclient_utils.py
File gclient_utils.py (right):

https://codereview.chromium.org/209393006/diff/2/gclient_utils.py#newcode43
gclient_utils.py:43: """Print any accumulated warnings."""
On 2014/03/24 17:53:06, M-A Ruel wrote:
> Prints

Done.

https://codereview.chromium.org/209393006/diff/2/gclient_utils.py#newcode51
gclient_utils.py:51: """Add the given warning message to the list of accumulated
warnings."""
On 2014/03/24 17:53:06, M-A Ruel wrote:
> Adds

Done.

https://codereview.chromium.org/209393006/diff/2/gclient_utils.py#newcode52
gclient_utils.py:52: _WARNINGS.append(msg)
On 2014/03/24 17:53:06, M-A Ruel wrote:
> In theory you'd need a lock. In practice, it's not a big deal.

My understanding is that list.append is thread-safe.  I guess we could still run
into trouble if we were running PrintWarnings throughout, but I think this is
okay.

[borenet, 2014-03-24 18:33:22]

The CQ bit was checked by borenet@google.com

[commit-bot: I haz the power, 2014-03-24 18:33:28]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/borenet@google.com/209393006/30001

[commit-bot: I haz the power, 2014-03-24 18:35:24]

Change committed as 258982