Comment 13 for bug 1569064

This will make networking's output go to the console as well:

sudo mkdir -p /etc/systemd/system/networking.service.d
printf '[Service]\nStandardOutput=journal+console\nStandardError=journal+console\n' | sudo tee /etc/systemd/system/networking.service.d/debug.conf

(I. e. do this before you set up the box to hang on networking). After a reboot, you should then be able to see what's going on in "nova console-log".