两种except，一种要导入，一种要写model。主要看个人习惯。

参考URL：
https://blog.csdn.net/dqchouyang/article/details/78246598

一，导入ObjectDoesNotExist

导入from django.core.exceptions import ObjectDoesNotExist，我感觉好点。

import os
import django
from django.core.exceptions import ObjectDoesNotExist

try:
     site_item = Site.objects.get(name=site)
except ObjectDoesNotExist as e:
     print(e)

二，和model关联DoesNotExist

不导入，但要和model绑定

try:
     site_item = Site.objects.get(name=site)
except Site.DoesNotExist as e:
     print(e)

随便pick!