output says "OS packages installation successful", exit code is 1

[raphael-proust]

Using the ocaml/opam:debian-testing-opam docker image in a CI, I have jobs where opam depext indicates success via stdout but failure via its exit code.

https://gitlab.com/nomadic-labs/data-encoding/-/jobs/1963430311
https://gitlab.com/nomadic-labs/data-encoding/-/jobs/1965645560

Success can be shown via "OS packages installation successful" or "All required OS packages found" (depending on the some caching of installed things).

The command that causes the issue is

opam install . --dry-run --deps-only --locked --with-test --with-doc --yes | awk '/-> installed/{print $3}' | xargs opam depext -iy

From https://gitlab.com/gasche/gitlab-ocaml-ci-example/-/blob/main/.gitlab-ci.yml

The command is somewhat outdated but does it explain the discrepancy between the output and the exit code?