[faiproject/fai] 49ae9b: we need "..." for variable expansion

[Mrfai]

  Branch: refs/heads/master
  Home:   https://github.com/faiproject/fai
  Commit: 49ae9b855380ed8831f3da939a8d4e1017b16010
      https://github.com/faiproject/fai/commit/49ae9b855380ed8831f3da939a8d4e1017b16010
  Author: Thomas Lange <lange at debian.org>
  Date:   2022-05-28 (Sat, 28 May 2022)

  Changed paths:
    M lib/fetch-basefile

  Log Message:
  -----------
  we need "..." for variable expansion