How to display app logs in nginx-unit docker?

Question

I am using the official nginx unit docker image, And I would like to run a hello world wsgi application, and being able to print stuff on docker-compose output.

How can I do that ?

Here the hello world:

print('DURING INITIAL SETUP')

def application(environ, start_response):
  print('DURING REQUEST')
  start_response('200 OK', [('Content-Type', 'text/plain')])
  yield b'Hello, World!\n'

But nothing is ever written to the output... (I also tried writing directly to /proc/1/fd/1, but missing permissions)