Comment 9 for bug 1652410

It's because you're using the fish shell instead of the more common bash shell. If I understand correctly, the fish translation of Vej's command is:

  env DEJA_DUP_DEBUG=1 deja-dup --backup | tail -n 1000 > /tmp/deja-dup.log

or:

  set -x DEJA_DUP_DEBUG 1
  deja-dup --backup | tail -n 1000 > /tmp/deja-dup.log