[py_utils] Add empty and optional context managers.

[py_utils] Add empty and optional context managers.

Review-Url: https://codereview.chromium.org/2585763004
Committed: https://chromium.googlesource.com/external/github.com/catapult-project/catapult/+/2c95066149e88b00bea89ac25599cbd8f931de0d

[jbudorick, 2016-12-17 00:27:36]

jbudorick@chromium.org changed reviewers:
+ nednguyen@google.com, rnephew@chromium.org

[rnephew (Reviews Here), 2016-12-17 00:39:57]

non-owner lgtm with one question.

https://codereview.chromium.org/2585763004/diff/1/common/py_utils/py_utils/co...
File common/py_utils/py_utils/contextlib_ext.py (right):

https://codereview.chromium.org/2585763004/diff/1/common/py_utils/py_utils/co...
common/py_utils/py_utils/contextlib_ext.py:9: def Empty():
What exactly is the use case for an empty context manager?

[nednguyen, 2016-12-17 12:22:42]

lgtm

[jbudorick, 2016-12-19 15:57:55]

https://codereview.chromium.org/2585763004/diff/1/common/py_utils/py_utils/co...
File common/py_utils/py_utils/contextlib_ext.py (right):

https://codereview.chromium.org/2585763004/diff/1/common/py_utils/py_utils/co...
common/py_utils/py_utils/contextlib_ext.py:9: def Empty():
On 2016/12/17 00:39:57, rnephew (Reviews Here) wrote:
> What exactly is the use case for an empty context manager?

Good point. I've used it elsewhere for a more hand-rolled implementation of
optional
(https://codesearch.chromium.org/chromium/src/build/android/test_runner.py?rcl...),
but with the implementation of Optional below, I'm not entirely sure what the
use of Empty would be. Removing for now, will add back later if it becomes
necessary.

[jbudorick, 2016-12-19 15:58:33]

The CQ bit was checked by jbudorick@chromium.org

[jbudorick, 2016-12-19 15:58:34]

The patchset sent to the CQ was uploaded after l-g-t-m from
nednguyen@google.com, rnephew@chromium.org
Link to the patchset: https://codereview.chromium.org/2585763004/#ps20001
(title: "rnephew comment")

[commit-bot: I haz the power, 2016-12-19 15:58:42]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-12-19 16:17:15]

CQ is committing da patch.

Bot data: {"patchset_id": 20001, "attempt_start_ts": 1482163113723970,
"parent_rev": "f394e56d288846ae3557dfd502506413c0f6a9ce", "commit_rev":
"2c95066149e88b00bea89ac25599cbd8f931de0d"}

[commit-bot: I haz the power, 2016-12-19 16:17:17]

Description was changed from

==========
[py_utils] Add empty and optional context managers.
==========

to

==========
[py_utils] Add empty and optional context managers.

Review-Url: https://codereview.chromium.org/2585763004
Committed:
https://chromium.googlesource.com/external/github.com/catapult-project/catapu...
==========

[commit-bot: I haz the power, 2016-12-19 16:17:19]

Committed patchset #2 (id:20001) as
https://chromium.googlesource.com/external/github.com/catapult-project/catapu...