add_dmesg() {
  local got_log=
  echo '** Kernel log:' >&3
  if [ "$(cat /proc/sys/kernel/dmesg_restrict)" = 0 ]; then
    dmesg > >(tail -n 100 >&3) && got_log=y
  elif command -v sudo >/dev/null; then
    yesno "Use sudo to read the kernel log? " yep
    if [ "$REPLY" = yep ]; then
      sudo dmesg > >(tail -n 100 >&3) && got_log=y
    fi
  fi
  test "$got_log" || echo 'Unable to read kernel log; any relevant messages should be attached' >&3
  echo >&3
}

ask_dmesg() {
  # Remind the user to attach the kernel log.  This should also trigger
  # a reminder in some MUAs if the user tries to send without it.
  echo '** Kernel log: boot messages should be attached' >&3
  echo >&3
}