The following revision refers to this bug:
  https://chromium.googlesource.com/infra/infra/+/f83404cee529c9b121ab28ff88a07fcfaba2ff8e

commit f83404cee529c9b121ab28ff88a07fcfaba2ff8e
Author: Roberto Carrillo <robertocn@google.com>
Date: Tue Apr 03 22:46:52 2018

[cr-audit-commits] Make message empty on passing rule.

Rules are expected to set the .Message field of the RuleResult only in
case of failure. The OnlyModifiesVersionFile in releasebot_rules.go was
setting it regardless of whether the rule failed, thus making the
display in the status page, inaccurate.

R=stgao,chanli

Bug:  821467 
Change-Id: Ib761c0dab59c1976bb7fd625a565f000b0312950
Reviewed-on: https://chromium-review.googlesource.com/992996
Commit-Queue: Roberto Carrillo <robertocn@chromium.org>
Reviewed-by: Shuotao Gao <stgao@chromium.org>

[modify] https://crrev.com/f83404cee529c9b121ab28ff88a07fcfaba2ff8e/go/src/infra/appengine/cr-audit-commits/app/releasebot_rules.go
[modify] https://crrev.com/f83404cee529c9b121ab28ff88a07fcfaba2ff8e/go/src/infra/appengine/cr-audit-commits/app/releasebot_rules_test.go