Ignore useless error messages.
Ignore useless error messages.

I suspect they are generated indirectly by appstats.

R=csharp@chromium.org
BUG=

Review URL: https://codereview.appspot.com/36200043

pombreda/swarming,luci/luci-py,pombreda/swarming,pombreda/swarming,madecoste/swarming,pombreda/swarming,madecoste/swarming,luci/luci-py,luci/luci-py,madecoste/swarming,madecoste/swarming,luci/luci-py