reproducible archlinux: the job name/number should be part of the session name so we can kill all previous sessions from that job easily

reproducible archlinux: follow up on 321db951 but revert the conditions to fail loudly and silently, to confirm the observations…

reproducible archlinux: abort silently if schroot session unmounting fails on pgg verification failure… (work in progress)

reproducible archlinux: detect if schroot session cannot be closed properly, then retry, else abort loudly

reproducible archlinux: fix two subtle bugs, preventing the packages list to be updated and causing always the last repo to be choosen

This reverts commit a790cbd5.