gistfile1.py

from django.conf import settings
from django.db.models import get_models, FileField
from django.core.files.storage import get_storage_class

STORAGE = get_storage_class(getattr(settings, "STORAGE", settings.DEFAULT_FILE_STORAGE))

for model in get_models():
    for field in model._meta.fields:
        if isinstance(field, FileField) and not isinstance(field.storage, STORAGE):
            FileField(verbose_name=field.verbose_name, upload_to=field.upload_to, name=field.name).\
                contribute_to_class(model, field.name)