When an HTTP exception information is logged, no information is sent by
default. Add an helper function to manually extract interesting information
to append it to the exception type.

Also disable another pylint warning.

TEST=manual test
BUG=none

Review URL: http://codereview.chromium.org/5303002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@67306 0039d316-1c4b-4281-b951-d872f2087c98