A common mistake in django is to make a model change but forget to run makemigrations to generate a migration for the model change. Sometimes it is not entirely obvious when this need to happen. For example, let's say I'm using the django-extensions library and I define a model like:

# models.py

from django.db import models
from django_extensions.db.models import TimeStampedModel

class MyModel(TimeStampedModel, models.Model):
    pass

In this situation, upgrading django-extensions to a new version might require me to regenerate the migrations in my app, even though I haven't made any changes to models.py and overlooking this could generate unexpected results.

Fortunately there is a simple thing I can do to detect and warn if this happens: If I run

python manage.py makemigrations --check

in my CI build, this will cause the build to fail if my migrations are out of sync with the models, warning me about the problem.