Python 为什么我收到这个 Django 自定义命令错误：'datetime.timezone' 没有属性'now'

当我试图在Django中运行这个删除超过30天的访客帐户的定制命令时，为什么我收到错误消息"‘Datetime.timezone’没有属性‘Now’"？它可以在views.py中的其他地方工作，我在那里以同样的方式导入了它.由于命令位于不同的文件夹中，我是否必须以不同的方式导入它？(管理/命令/)

from django.core.management.base import BaseCommand
from datetime import timezone, timedelta

from gridsquid.models import User, Tile

DEFAULT_TILE_IMG_NAME = "defaultsquid.svg"
MAX_GUEST_ACCOUNT_DAYS = 30

class Command(BaseCommand):
    def handle(self, *args, **options):
        """
        Deletes all guest user accounts and their media if older than MAX_GUEST_ACCOUNT_DAYS
        """
        # Get all guest accounts created before the limit
        expired_guests_count = User.objects.filter(guest=True).filter(date_joined__lt=timezone.now()-timedelta(days=MAX_GUEST_ACCOUNT_DAYS)).count()
        expired_guests = User.objects.filter(guest=True).filter(date_joined__lt=timezone.now()-timedelta(days=MAX_GUEST_ACCOUNT_DAYS))
        
        for guest in expired_guests:
            tiles = Tile.objects.select_related("user").filter(user=guest).all()
            for tile in tiles:
                # Delete image if not default image
                if DEFAULT_TILE_IMG_NAME not in tile.image.url:
                    tile.image.delete()
                # Delete audio file if there is one
                if tile.audio is not None:
                    tile.audio.delete()
            # Delete guest account
            guest.delete()