downgrading to previous migration django
Reversing migrations¶
Migrations can be reversed with migrate by passing 
the number of the previous migration.
For example, to reverse migration books.0003:
$ python manage.py migrate books 0002
Operations to perform:
  Target specific migration: 0002_auto, from books
Running migrations:
  Rendering model states... DONE
  Unapplying books.0003_auto... OK
