How to do it...

To use the system-check framework, go through these steps:

1. Create the checks.py file with the following content:

# myproject/apps/viral_videos/checks.py
from textwrap import dedent

from django.core.checks import Warning, register, Tags


@register(Tags.compatibility)
def settings_check(app_configs, **kwargs):
    from django.conf import settings

    errors = []

    if not settings.ADMINS:
        errors.append(
            Warning(
                dedent("""
                    The system admins are not set in the project 
                     settings
                """),
                obj=settings,
                hint=dedent("""
                    In order to receive notifications when new 
                     videos are created, define system admins 
                     in your settings, like:
        
                    ADMINS = (
                        ("Admin", "administrator@example.com"),
                    )
                """),
                id="viral_videos.W001",
            )
        )

    return errors

2. Import the checks in the ready() method of the app configuration as follows:

# myproject/apps/viral_videos/apps.py
from django.apps import AppConfig
from django.utils.translation import ugettext_lazy as _


class ViralVideosAppConfig(AppConfig):
    name = "myproject.apps.viral_videos"
    verbose_name = _("Viral Videos")

    def ready(self):
        from .signals import inform_administrators
        from .checks import settings_check

3. To try the check that you just created, remove or comment out the ADMINS setting and then run the check management command in your virtual environment:
   

(env)$ python manage.py check
System check identified some issues:

WARNINGS:
<Settings "myproject.settings.dev">: (viral_videos.W001)
The system admins are not set in the project settings

HINT:
In order to receive notifications when new videos are
created, define system admins in your settings, like:

ADMINS = (
    ("Admin", "administrator@example.com"),
)


System check identified 1 issue (0 silenced).