monorobot

10 lines of failure log are disaplayed in the error DMmessage (#194) * 10 lines of failure log are disaplayed in the message * put the log in an attachment * Update lib/slack.ml Co-authored-by: José Nogueira <thatportugueseguy@users.noreply.github.com> * Update lib/slack.ml Co-authored-by: José Nogueira <thatportugueseguy@users.noreply.github.com> * cleanup --------- Co-authored-by: Emile Trotignon <emile.trotignon@ahrefs.com> Co-authored-by: José Nogueira <thatportugueseguy@users.noreply.github.com>