Django admin and SQLite: database disk image is malformed

Only three steps.

1. delete db.sqlite3 and all migrations files
2. run python manage.py makemigrations
3. run python manage.py migrate

As Joel pointed out "SQLite3 database or disk is full / the database disk image is malformed" has a solution in its comment sections (https://askubuntu.com/questions/30185/banshee-encountered-a-fatal-error-sqlite-error-11-database-disk-image-is-malfo). Thank you Joel Goldstick for the help!