notify the swh-devel mailing list of build failures for daily CI jobs

Failures of daily CI jobs are easy to overlook right now because the notifications are sent only to #swh-devel on IRC at 5 a.m. in the morning.

I'm thinking of jobs like swh-docker-dev (see this recent failure) and the daily rebuild of docs.s.o. But there might be more.

I'd like to receive notifications of those failures via the swh-devel mailing list. That way they can be picked up by whomever feel like, and a follow-up on list can be sent to notify others they have been fixed (or are being worked on at least).

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Migrated from T2684 (view on Phabricator)