Otherwise, the program continues, and an exception is printed.
The message is still there, but easy to miss.

R=andybons@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2004303003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@300674 0039d316-1c4b-4281-b951-d872f2087c98