Use the config

STORAGES = {
    "default": {
        "BACKEND": "storages.backends.s3.S3Storage",
    },
    "staticfiles": {
        "BACKEND": "storages.backends.s3.S3Storage",
    },
}

instead of

DEFAULT_FILE_STORAGE = "storages.backends.s3.S3Storage"
STATICFILES_STORAGE = "storages.backends.s3.S3Storage"