python manage.py shell

from django.contrib.auth.models import User

usr = User.objects.get(username='your username')
usr.set_password('raw password')
usr.save()

python manage.py changepassword <user_name>

>>> from django.contrib.auth.models import User
>>> u = User.objects.get(username='john')
>>> u.set_password('new password')
>>> u.save()