django.db.utils.OperationalError: (2003, "Can't connect to MySQL server on '127.0.0.1' (111)"
check your mysql server is running or not
restart the mysql server
I've installed NGINX, GUNICORN and my project properly on Ubuntu server, 
but when I run the project using
python manage.py runserver, I get the following error; 

django.db.utils.OperationalError: (2003, "Can't connect to MySQL server on '127.0.0.1' (111)"

Before, installing gunicorn, my site was running properly at my_public_ip_address:8000