milo: log failure to compute blamelist.
milo: log failure to compute blamelist.

Before, the error would only be seen in UI, making debugging harder.

R=2190fe9a39b4920ec7bd59c848ec5cccd163056f@chromium.org

Change-Id: I609687276deab2f70fbfb7deb1d19514634fc86f
Reviewed-on: https://chromium-review.googlesource.com/1037805
Reviewed-by: Ryan Tseng <2190fe9a39b4920ec7bd59c848ec5cccd163056f@chromium.org>
Commit-Queue: Andrii Shyshkalov <a30c74fa30536fe7ea81ed6dec202e35e149e1fd@chromium.org>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go