If cit is run with an unknown tool, print usage rather than throwing an exception

If cit is run with an unknown tool, print usage rather than throwing an exception

BUG=
TBR=hinoka

Committed: https://chromium.googlesource.com/chromium/tools/depot_tools/+/72decfedaa9650d843c2c4e9c0c0e1fcbe226331

[dsansome, 2016-07-27 04:25:02]

dsansome@chromium.org changed reviewers:
+ hinoka@chromium.org

[Ryan Tseng, 2016-08-01 23:14:02]

hinoka@google.com changed reviewers:
+ hinoka@google.com

[Ryan Tseng, 2016-08-01 23:14:03]

lgtm

[dsansome, 2016-08-02 03:33:47]

The CQ bit was checked by dsansome@chromium.org

[commit-bot: I haz the power, 2016-08-02 03:33:52]

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, 2016-08-02 03:39:40]

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

[commit-bot: I haz the power, 2016-08-02 03:39:41]

Try jobs failed on following builders:
  Depot Tools Presubmit on luci.infra.try (JOB_FAILED,
https://luci-milo.appspot.com/swarming/task/30622248defd0710)

[dsansome, 2016-08-02 03:52:30]

On 2016/08/02 03:39:41, commit-bot: I haz the power wrote:
> Try jobs failed on following builders:
>   Depot Tools Presubmit on luci.infra.try (JOB_FAILED,
> https://luci-milo.appspot.com/swarming/task/30622248defd0710)

I think this failed because the LGTM was from hinoka@google.com, but only
hinoka@chromium.org is in OWNERS.
https://codereview.chromium.org/2194383003 to add all @google.com owners, and
I'll TBR this.

[dsansome, 2016-08-02 03:52:40]

Description was changed from

==========
If cit is run with an unknown tool, print usage rather than throwing an
exception

BUG=
==========

to

==========
If cit is run with an unknown tool, print usage rather than throwing an
exception

BUG=
TBR=hinoka
==========

[dsansome, 2016-08-02 03:52:44]

The CQ bit was checked by dsansome@chromium.org

[commit-bot: I haz the power, 2016-08-02 03:52:51]

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, 2016-08-02 03:55:49]

Description was changed from

==========
If cit is run with an unknown tool, print usage rather than throwing an
exception

BUG=
TBR=hinoka
==========

to

==========
If cit is run with an unknown tool, print usage rather than throwing an
exception

BUG=
TBR=hinoka

Committed:
https://chromium.googlesource.com/chromium/tools/depot_tools/+/72decfedaa9650...
==========

[commit-bot: I haz the power, 2016-08-02 03:55:50]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/tools/depot_tools/+/72decfedaa9650...