Home Automation is only useful if it's automatic. So with a proof of concept Python script I needed to turn it into a service. This is pretty easy with systemd. All you need is a "yourservicename.service" file in the /etc/systemd/system folder that calls your script.

Important parts on this are to name the correct user and file location in your service:

[Service]
Type=simple
User=pi
ExecStart=/usr/bin/python3 /home/pi/wemoswitch-to-mqtt/wemo-mqtt-control.py

[Install]
WantedBy=multi-user.target

Start it with systemctl (protip, you'll want to use systemctl status yourservicename.service to see if it had errors or is running correctly):

systemctl enable mqtt_porchlight.service
systemctl start mqtt_porchlight.service