start-stop script for this venv webserver is not working

Question

I have a small web server that I use for testing and I want to write a start-stop command for it so I can start and stop it with "service mysrv start" and "service mysrv stop"

manually I do this :

root@local:~# su - user
user@local:~$ . ~/mysrv/bin/activate
(mysrv) user@local:~$ python3 -m http.server --bind 127.0.0.1 --directory /home/user/mysrv/webroot 10800 > /dev/null 2>&1 &

this works

then I wrote the following

#!/bin/sh
### BEGIN INIT INFO
# Provides:          cdn-zp1-net
# Required-Start:    $remote_fs $syslog
# Required-Stop:     $remote_fs $syslog
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: Start daemon at boot time
# Description:       Enable service provided by daemon.
### END INIT INFO

NAME=mysrv 
USER=user
GROUP=users
WORKING_DIRECTORY=/home/user
VENV_PATH=". ~/mysrv/bin/activate"
COMMAND="/home/user/mysrv/bin/python3 -m http.server -b 127.0.0.1 -d /home/user/mysrv/webroot 10800"

PIDFILE=/var/run/$NAME.pid

start() {
    echo "Starting $NAME"
    cd $WORKING_DIRECTORY
    $VENV_PATH
    start-stop-daemon --start --quiet --pidfile $PIDFILE --make-pidfile --background --exec $COMMAND
}

stop() {
    echo "Stopping $NAME"
    start-stop-daemon --stop --quiet --pidfile $PIDFILE
    rm -f $PIDFILE
}

status() {
    if [ -r $PIDFILE ]; then
        echo "$NAME is running"
    else
        echo "$NAME is not running"
    fi
}


case "$1" in
    start)
        start
        ;;
    stop)
        stop
        ;;
    restart)
        stop
        start
        ;;
    *)
        echo "Usage: /etc/init.d/$NAME {start|stop|restart}"
        exit 1
        ;;
esac

exit 0

I tried all versions

source ~/mysrv/bin/activate

and

source /home/user/mysrv/bin/activate

but I just get a lot of errors

/etc/init.d/mysrv: 24: .: cannot open ~/mysrv/bin/activate: No such file

/etc/init.d/mysrv: 24: .: cannot open /home/user/mysrv/bin/activate: No such file

How should I solve this ?