Bootstrap does not be set to Django app

Bootstrap does not be set to my Django app.In google console,Failed to load resource: the server responded with a status of 404 (Not Found) bootflat.min.css error happens.I wrote in settings.py

BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
DEBUG =True

STATIC_URL = '/static/'

STATIC_ROOT = os.path.join(BASE_DIR, "static/")

STATICFILES_DIRS = [os.path.join(BASE_DIR,'bootflat.github.io'), ]

in PythonServer_nginx.conf

server {
    # the port your site will be served on
    listen      8000;
    # the domain name it will serve for
    server_name MyServerIPAdress; # substitute your machine's IP address or FQDN
    charset     utf-8;

    # max upload size
    client_max_body_size 75M;   # adjust to taste

    location /static {
        alias /home/ubuntu/PythonServer/PythonServer/accounts/static; # your Django project's static files - amend as required
    }

    # Finally, send all non-media requests to the Django server.
    location / {
        uwsgi_pass  django;
        include     /home/ubuntu/PythonServer/uwsgi_params; # the uwsgi_params file you installed
    }
}

I do not know why Bootstrap does not be set to my Django app.I run command python manage.py collectstatic but no error happens.How should I fix this?What should I write it?

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