Fixes this flake: https://build.chromium.org/p/chromium.infra/builders/infra-continuous-mac-10.9-64/builds/1729/steps/upload%20go%20bin/logs/stdio

BUG=

Review URL: https://codereview.chromium.org/1824223002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@299525 0039d316-1c4b-4281-b951-d872f2087c98