<filename>s3file/checks.py
from django.core.checks import Error
from django.core.files.storage import FileSystemStorage, default_storage


def storage_check(app_configs, **kwargs):
    if isinstance(default_storage, FileSystemStorage):
        return [
            Error(
                "FileSystemStorage should not be used in a production environment.",
                hint="Please verify your DEFAULT_FILE_STORAGE setting.",
                id="s3file.E001",
            )
        ]
    return []

<filename>s3file/checks.py
from django.core.checks import Error
from django.core.files.storage import FileSystemStorage, default_storage


def storage_check(app_configs, **kwargs):
    if isinstance(default_storage, FileSystemStorage):
        return [
            Error(
                "FileSystemStorage should not be used in a production environment.",
                hint="Please verify your DEFAULT_FILE_STORAGE setting.",
                id="s3file.E001",
            )
        ]
    return []
