Add an explicit Register() function to be called outside of this file.
Send the host fqdn to help know from where the exception comes. It is useful when a build slave throws an exception.

Review URL: http://codereview.chromium.org/2327003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@48455 0039d316-1c4b-4281-b951-d872f2087c98