All code is in the /app folder.
Make virtualenv, install requirements, then tell flask which app to use export FLASK_APP=app, then flask run, and don't forget to set export PYTHONPATH=./ as the flask CLI script is not in the same folder.
Go to directory of git repo.
On Ubuntu, install all necessary packages first: sudo apt install circus nginx python-pip chaussette mongodb python-opencv
Disable mongodb service (we run it ourselves): systemctl disable mongodb
(Probably I forgot some dependencies that I had already installed on the dev server)
Then install required python packages: pip install -r requirements.txt
Enable swap if numpy does not compile.
Make dirs: mkdir log && mkdir mongodb
Upload paintings. Set proper permissions.
Then symlink circus.service into /etc/systemd/system/circus.service and do systemctl --system daemon-reload.