/usr/bin/byobu-enable-prompt is in byobu 5.87-1.
This file is owned by root:root, with mode 0o755.
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 42 | #!/bin/sh -e
#
#    byobu-enable-prompt
#    Copyright (C) 2013-2014 Dustin Kirkland
#
#    Authors: Dustin Kirkland <kirkland@byobu.co>
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, version 3 of the License.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
[ "$SHELL" = "/bin/bash" ] || exit 1
PKG="byobu"
[ -r "$HOME/.byoburc" ] && . "$HOME/.byoburc"
[ -z "${BYOBU_PREFIX}" ] && export BYOBU_PREFIX="/usr" || export BYOBU_PREFIX
. "${BYOBU_PREFIX}/lib/${PKG}/include/common"
prompt="${BYOBU_CONFIG_DIR}/prompt"
printf ". ${BYOBU_PREFIX}/share/${PKG}/profiles/bashrc  #byobu-prompt#\n" > "$prompt"
$PKG-disable-prompt --no-reload "$1" || true
printf "[ -r $prompt ] && . $prompt   #byobu-prompt#\n" >> "$HOME/.bashrc"
if [ -n "$TMUX" ]; then
	tmux send-keys " . ~/.bashrc" \; send-keys Enter
else
	echo
	echo "You will need to reload your shell configuration for this to take effect..."
	echo "  . ~/.bashrc"
	echo
fi
# vi: syntax=sh ts=4 noexpandtab
 |