What's a zipapp?

virtualenv -p python3 venv
source ./venv/bin/activate
pip install Flask gunicorn

mkdir app
cd app
pip freeze > requirements.txt
pip install -t . -r requirements.txt
rm -rf ./__pycache__ ./*.dist-info

cp -r ../flaskr .
cd ..

python3 -m zipapp app -m 'gunicorn.app.wsgiapp:run' -p '/usr/bin/env python3'

You get an executable .pyz archive with all dependencies bundled inside.

ls -lh app.pyz

-rwxr--r--  1 user  user   4.0M Dec 18 09:38 app.pyz

file app.pyz

app.pyz: a /usr/bin/env python3 script executable (binary data)

./app.pyz flaskr:app

[2017-12-18 09:38:35 +0200] [39081] [INFO] Starting gunicorn 19.7.1
[2017-12-18 09:38:35 +0200] [39081] [INFO] Listening at: http://127.0.0.1:8000 (39081)
[2017-12-18 09:38:35 +0200] [39081] [INFO] Using worker: sync
[2017-12-18 09:38:35 +0200] [39084] [INFO] Booting worker with pid: 39084