Comment 6 for bug 67996

Looking into x11-common.preinst it looks like this is the fragment that causes the trouble:

  # We need to remove /usr/X11R6/bin so we can replace it with a symlink
  if [ -d "/usr/X11R6/bin" ] && [ ! -L /usr/X11R6/bin ]; then
    if ! rmdir "/usr/X11R6/bin"; then
      run db_fset x11-common/x11r6_bin_not_empty seen false
      run db_input critical x11-common/x11r6_bin_not_empty
      run db_go
      exit 1
    fi
  fi

I don't think it should fail but issue a message and move the old dir aside to prevent upgrades from failing.

Cheers,
 Michael