This CQ run failed, but still successfully committed some CLs:
    https://luci-milo.appspot.com/buildbot/chromeos/master-paladin/17253

During the CommitQueueHandleChanges stage, two CLs encountered an
unexpected Gerrit response.  Here are the relevant log entries:

15:43:37: INFO: RunCommand: git remote update cros-internal in /b/c/cbuild/repository/src/private-overlays/overlay-reef-private
15:43:37: INFO: RunCommand: git rebase refs/remotes/cros-internal/master in /b/c/cbuild/repository/src/private-overlays/overlay-reef-private
15:43:37: INFO: RunCommand: git push https://chrome-internal-review.googlesource.com/chromeos/overlays/overlay-reef-private HEAD:master in /b/c/cbuild/repository/src/private-overlays/overlay-reef-private
15:44:12: WARNING: Change *530641 was pushed without errors, but gerrit is reporting it with status "NEW" (expected "MERGED").
15:44:12: ERROR: Gerrit likely was unable to merge change *530641.
15:44:12: INFO: Running cidb query on pid 13939, repr(query) starts with <sqlalchemy.sql.expression.Insert object at 0x7f901608da10>
15:44:13: INFO: RunCommand: git remote update cros in /b/c/cbuild/repository/src/overlays
15:44:13: INFO: RunCommand: git rebase refs/remotes/cros/master in /b/c/cbuild/repository/src/overlays
15:44:13: INFO: RunCommand: git push https://chromium-review.googlesource.com/chromiumos/overlays/board-overlays HEAD:master in /b/c/cbuild/repository/src/overlays
15:44:46: WARNING: Change 832962 was pushed without errors, but gerrit is reporting it with status "NEW" (expected "MERGED").
15:44:46: ERROR: Gerrit likely was unable to merge change 832962.
15:44:46: INFO: Running cidb query on pid 13939, repr(query) starts with <sqlalchemy.sql.expression.Insert object at 0x7f901608d2d0>

Despite the message, the CLs were, in fact, committed to the tree.

The event had some undesirable side-effects:
 1) Normally, the commit message includes information such as
    "Reviewed-on:" and "Reviewed-by:".  In this particular case,
    the extra commit message fields are omitted.
 2) Gerrit sees the CLs as not yet merged, so the CQ will retry
    them freely.  In that case, the CLs fail with a message like
    "CL:123456 had no changes after rebasing to ToT."  So, the CLs
    can't be closed.