Catch exception if --adb-key-files file does not exist and log warning.

Catch exception if --adb-key-files file does not exist and log warning.

BUG=

Committed: https://crrev.com/101326f95ee0cb7a68d1e337d9966fe4bc9cf9cc
Cr-Commit-Position: refs/heads/master@{#318999}

[navabi, 2015-03-04 00:20:05]

navabi@google.com changed reviewers:
+ friedman@chromium.org, jbudorick@chromium.org, luqui@chromium.org

[navabi, 2015-03-04 00:20:06]

Please review with this CL: https://codereview.chromium.org/976913002/

[jbudorick, 2015-03-04 00:20:46]

lgtm w/ nit

https://codereview.chromium.org/975963002/diff/1/build/android/provision_devi...
File build/android/provision_devices.py (right):

https://codereview.chromium.org/975963002/diff/1/build/android/provision_devi...
build/android/provision_devices.py:14: import glob
nit: remove this

[navabi, 2015-03-04 00:25:47]

The CQ bit was checked by navabi@google.com

[navabi, 2015-03-04 00:25:48]

The patchset sent to the CQ was uploaded after l-g-t-m from
jbudorick@chromium.org
Link to the patchset: https://codereview.chromium.org/975963002/#ps20001 (title:
"Remove unnecessary import glob.")

[commit-bot: I haz the power, 2015-03-04 00:27:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/975963002/20001

[commit-bot: I haz the power, 2015-03-04 02:14:38]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-03-04 02:15:27]

Patchset 2 (id:??) landed as
https://crrev.com/101326f95ee0cb7a68d1e337d9966fe4bc9cf9cc
Cr-Commit-Position: refs/heads/master@{#318999}