coqbot gives bug minimizer non-existent urls

[JasonGross]

@Zimmi48 do you know what's up with the following failures?

• ci-sf failed because https://gitlab.com/coq/coq/-/jobs/1991212828/artifacts/download is a 404, idk what's up here
• ci-itauto failed because https://gitlab.com/coq/coq/-/jobs/1991212857/artifacts/download is a 404
• ci-relation_algebra failed because https://gitlab.com/coq/coq/-/jobs/1991212883/artifacts/download is a 404
• ci-metacoq failed because https://gitlab.com/coq/coq/-/jobs/1991212867/artifacts/download is a 404

Originally posted by @JasonGross in https://github.com/coq/coq/issues/15518#issuecomment-1018009004

[Zimmi48]

Sorry for reacting so late.

These jobs (from a pipeline on the base branch) do not have artifacts because they were skipped (although I do not know why they got skipped by GitLab CI, but this might be related to this issue: https://gitlab.com/gitlab-org/gitlab/-/issues/217129).

Should we make the minimizer more robust to this situation?

[SkySkimmer]

I suspect it's related to build:base getting restarted from "runner system failure"

[Zimmi48]

This explanation would make a lot of sense because there is a good match between which job was skipped and which job depends on build:base in this screenshot:

However, outside this screenshot there are several other jobs that depend on build:base and yet were not skipped, so there might be an additional factor at stake.