Where do logs go?

I have burp-ui set up under gunicorn as follows

root@rubicon:~# cat /etc/gunicorn.d/burp-ui
CONFIG = {
    'working_dir': '/',
    'args': (
        '--bind=127.0.0.1:5000',
        '--user=burpui',
        '--workers=5',
        '--worker-class=eventlet',
        '--access-logfile=/var/log/gunicorn/burp-ui_access.log',
        '--error-logfile=/var/log/gunicorn/burp-ui_error.log',
        '--log-level=debug',
        'burpui:init(conf="/etc/burp/burpui.cfg",debug=True)',
    ),
}

and now gunicorn DEBUG and INFO level messages go into burp-ui_error.log, while the burp-ui_access.log is similar to a web server access log.

But I can't find the debug and info level messages from burpui anywhere!