I constantly get this error while running apt-get upgrade or apt-get udpate linux-headers... on RPI3. A thread was started on GitHub relating this issue: https://github.com/meefik/linuxdeploy/issues/869#issuecomment-344967347 *Je communique aussi en français.
Thanks for your bug report. Unfortunately, this is not related to exo or Xfce in general. Marking as WONTFIX.