Comment # 2 on bug 1060111 from Dr. Werner Fink

/etc/bash_completion.d/lyx is using

  have lyx &&
  _lyx()
  {

and so on

  /etc/bash_completion.d/bumblebee
  /etc/bash_completion.d/grub
  /etc/bash_completion.d/ufw.sh
  /etc/bash_completion.d/fcoeadm
  /etc/bash_completion.d/lldpad
  /etc/bash_completion.d/lldptool
  /etc/bash_completion.d/tuxpaint-completion.bash

and upstream of bash-completion has decided to undefine this internal shell
function