/usr/share/bash-completion/completions/script is in bsdutils 1:2.31.1-0.4ubuntu3.
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  | _script_module()
{
	local cur prev OPTS
	COMPREPLY=()
	cur="${COMP_WORDS[COMP_CWORD]}"
	prev="${COMP_WORDS[COMP_CWORD-1]}"
	case $prev in
		'-c'|'--command')
			compopt -o bashdefault
			COMPREPLY=( $(compgen -c -- $cur) )
			return 0
			;;
		'-h'|'--help'|'-V'|'--version')
			return 0
			;;
	esac
	case $cur in
		'=')
			cur=${cur#=}
			;;
		-*)
			OPTS="--append
				--command
				--return
				--flush
				--force
				--quiet
				--timing=
				--version
				--help"
			COMPREPLY=( $(compgen -W "${OPTS[*]}" -- $cur) )
			return 0
			;;
	esac
	local IFS=$'\n'
	compopt -o filenames
	COMPREPLY=( $(compgen -f -- $cur) )
	return 0
}
complete -F _script_module script
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