/usr/share/bash-completion/completions/renice is in bsdutils 1:2.27.1-6ubuntu3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41  | _renice_module()
{
	local cur prev OPTS
	COMPREPLY=()
	cur="${COMP_WORDS[COMP_CWORD]}"
	prev="${COMP_WORDS[COMP_CWORD-1]}"
	case $prev in
		'-g'|'--pgrp')
			local PGRP
			PGRP=$(ps -ax -opgrp | sed '1d')
			COMPREPLY=( $(compgen -W "$PGRP" -- $cur) )
			return 0
			;;
		'-n'|'--priority')
			COMPREPLY=( $(compgen -W "{-20..20}" -- $cur) )
			return 0
			;;
		'-p'|'--pid')
			local PIDS
			PIDS=$(for I in /proc/[0-9]*; do echo ${I##"/proc/"}; done)
			COMPREPLY=( $(compgen -W "$PIDS" -- $cur) )
			return 0
			;;
		'-u'|'--user')
			COMPREPLY=( $(compgen -u -- $cur) )
			return 0
			;;
		'-h'|'--help'|'-V'|'--version')
			return 0
			;;
	esac
	OPTS="--pgrp
		--priority
		--pid
		--user
		--help
		--version"
	COMPREPLY=( $(compgen -W "${OPTS[*]}" -- $cur) )
	return 0
}
complete -F _renice_module renice
 |