Improve logging in case of email sending failure. Failure message should be visible in buildbot UI instead of just the logs.
Pull request: https://github.com/WebKit/WebKit/pull/10816
<rdar://problem/106374996>
Committed 261423@main (c58a5c443d87): <https://commits.webkit.org/261423@main> Reviewed commits have been landed. Closing PR #10816 and removing active labels.