> isn't invoke returning an exact integer ?

No.  "invoke" raises an exception if the child's exit code != 0.
Otherwise you get #t.

"system*" returns the exit code - might want to use that instead.
(just replace the text "invoke" by "system*")

> Maybe tryton-admin insn't seeing the env var and promtping to ask for its
> interaction ?
>
>
> How am I supposed to use setenv, exactly ?

Looks fine to me.

Just exit with (primitive-exit 0) in the end :)