django - CommandError: No installed app with label 'inheritance', Are you sure your INSTALLED_APPS setting is correct? -

installed_apps = (     'django.contrib.admin',     'django.contrib.auth',     'django.contrib.contenttypes',     'django.contrib.sessions',     'django.contrib.messages',     'django.contrib.staticfiles',     'inheritance', ) 

this way have mentioned app 'inheritance' in setting file of django project . there have followed in order rid of error

i getting error when running command

python manage.py sqlall inheritance/ 

this directory structure

documentation/    ├── abstract/    ├── db.sqlite3    ├── documentation/    |── inheritance/    └── manage.py