Print response from the server on HTTP errors from Rietveld

Print response from the server on HTTP errors from Rietveld

This will make explanation provided by Rietveld visible to the user, e.g.
"Request to https://codereview.chromium.org/1386443003/edit_flags failed: Cannot
set commit on an issue that does not have a commit queue".

R=phajdan.jr@chromium.org
BUG=529339
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=297009

[Sergiy Byelozyorov, 2015-10-05 13:17:47]

sergiyb@chromium.org changed reviewers:
+ jrobbins@chromium.org

[Sergiy Byelozyorov, 2015-10-05 13:17:47]

Also adding Jason in case he knows why we shouldn't print this output.

[Paweł Hajdan Jr., 2015-10-05 13:42:56]

LGTM

[jrobbins, 2015-10-05 15:29:26]

lgtm

[Sergiy Byelozyorov, 2015-10-05 15:40:13]

The CQ bit was checked by sergiyb@chromium.org

[commit-bot: I haz the power, 2015-10-05 15:40:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1387833002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1387833002/1

[Sergiy Byelozyorov, 2015-10-05 15:41:00]

sergiyb@chromium.org changed reviewers:
+ tandrii@chromium.org

[Sergiy Byelozyorov, 2015-10-05 15:41:09]

+tandrii for OWNERS

[tandrii(chromium), 2015-10-05 15:43:49]

rs lgtm

[commit-bot: I haz the power, 2015-10-05 15:45:20]

Committed patchset #1 (id:1) as
http://src.chromium.org/viewvc/chrome?view=rev&revision=297009