This avoids build errors like at http://build.chromium.org/p/tryserver.chromium/builders/linux_clang/builds/64851/steps/update/logs/stdio (search for mtpd).

BUG=none


Review URL: https://chromiumcodereview.appspot.com/11417059

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@168521 0039d316-1c4b-4281-b951-d872f2087c98