When a developer runs download_from_google_storage, and they don't have a .boto
file, the tool automatically runs "gsutil config" to create one for them.
Unfortunately, a side consequence is that if a bot runs the script, and it has
a boto file that 403's, then it would run "gsutil config" which moves the .boto
to .boto.bak, and creates an empty .boto file.  This should not be the intended
action.

This CL changes so that "gsutil config" is not called, but instead just fails
with a message telling the dev to run that command.

TBR=maruel@chromium.org

Review URL: https://codereview.chromium.org/16072023

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@203824 0039d316-1c4b-4281-b951-d872f2087c98