upload.py returns them as string, eventually leading to a crash.

R=iannucci@chromium.org
BUG=265546

Review URL: https://chromiumcodereview.appspot.com/21020008

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@214247 0039d316-1c4b-4281-b951-d872f2087c98