KeyError: SECRET_KEY not set

KeyError: SECRET_KEY not set

$ DJANGO_SETTINGS_MODULE=project.settings python manage.py runserver
Traceback (most recent call last):
  ...
KeyError: 'SECRET_KEY'

Why this happens

Reading os.environ['SECRET_KEY'] without default when env variable missing.

Fix

Provide default or fail clearly.

Wrong code

SECRET_KEY = os.environ['SECRET_KEY']

Fixed code

SECRET_KEY = os.environ.get('SECRET_KEY', 'dev-secret')
# In production, ensure env var is set