[faiproject/fai] 61051b: better error message, Closes: #1005745

[Mrfai]

  Branch: refs/heads/master
  Home:   https://github.com/faiproject/fai
  Commit: 61051b1cac6fdec5022c155eb4e387ab5d232fae
      https://github.com/faiproject/fai/commit/61051b1cac6fdec5022c155eb4e387ab5d232fae
  Author: Thomas Lange <lange at debian.org>
  Date:   2022-05-26 (Thu, 26 May 2022)

  Changed paths:
    M lib/setup-storage/Exec.pm

  Log Message:
  -----------
  better error message, Closes: #1005745