Ubuntu GNOME 17.04: wi-fi not working -- mac address keeps changing?

So Jesse discovered a solution and I'm going to share it here in answer form as clearly as I can muster. This fixed wifi for me using a Panda Wireless USB wifi adapter on Ubuntu 17.04:

For privacy reasons, the default settings for Ubuntu 17.04's network manager (ALL flavours, not just GNOME) cause the MAC address of the Wifi device to change constantly. To fix this, you just have to create a new config file as outlined below and then restart the network-manager service.

Open a terminal and run:

sudo tee /etc/NetworkManager/conf.d/wifi.scan-rand-mac-address.conf > /dev/null <<EOF
[device]
wifi.scan-rand-mac-address=no
EOF
sudo service network-manager restart

and wifi should work again! (unless something else is wrong).

This fix should work even on a live CD/USB session.