This is currently set up to work with a single door to a single hackerspace, therefore YMMV.
(This assumes Raspbian)
Configure serial at /dev/ttyAMA0 with raspi-config, choose Interfacing options -> Serial, disable login shell over serial, enable serial hardware.
Alternatively remove the console=serial0 entry from /boot/cmdline.txt.
Give the user permissions to the required devices and install required packages (as root):
# gpasswd -a user dialout
# gpasswd -a user gpio
# apt-get install python3-venv python3-dev
Create virtual environment and install pip packages
$ python3 -m venv venv
$ source venv/bin/activate
$ pip install -r requirements.txt
Create settings.py based on the example file, edit to taste and test:
$ cp settings.py.example settings.py
$ your_favorite_editor settings.py
$ ./run.sh
Edit renksu.service.example to set correct path and install (as root):
# cp renksu.service.example /etc/systemd/system/renksu.service
# systemctl enable renksu