在不影响旧迁移文件的情况下，用Django-2升级wagtail-2。我得到这个'NoneType‘对象没有属性'is_relation’

Question

我正在尝试将wagtail-1.9升级到wagtail-2.0，将Django-1.10.6升级到Django-2.0，但我得到了这个错误。

    delay = not old_field.is_relation
    AttributeError: 'NoneType' object has no attribute 'is_relation'

我不想删除或重置我的旧迁移文件，因为如果我删除旧迁移文件或重置它，我将丢失数据。

这是错误的全部细节。

Operations to perform:
  Apply all migrations: admin, auth, contenttypes, core, faq, home, mailqueue, sessions, taggit, testimonial, wagtailadmin, wagtailcore, wagtaildocs, wagtailembeds, wagtailforms, wagtailimages, wagtailredirects, wagtailsearch, wagtailusers
Traceback (most recent call last):
      File "manage.py", line 11, in <module>
        execute_from_command_line(sys.argv)
      File "/home/razia/.virtualenvs/web-dj2/lib/python3.6/site-packages/django/core/management/__init__.py", line 371, in execute_from_command_line
        utility.execute()
      File "/home/razia/.virtualenvs/web-dj2/lib/python3.6/site-packages/django/core/management/__init__.py", line 365, in execute
        self.fetch_command(subcommand).run_from_argv(self.argv)
      File "/home/razia/.virtualenvs/web-dj2/lib/python3.6/site-packages/django/core/management/base.py", line 288, in run_from_argv
        self.execute(*args, **cmd_options)
      File "/home/razia/.virtualenvs/web-dj2/lib/python3.6/site-packages/django/core/management/base.py", line 335, in execute
        output = self.handle(*args, **options)
      File "/home/razia/.virtualenvs/web-dj2/lib/python3.6/site-packages/django/core/management/commands/migrate.py", line 159, in handle
        pre_migrate_state = executor._create_project_state(with_applied_migrations=True)
      File "/home/razia/.virtualenvs/web-dj2/lib/python3.6/site-packages/django/db/migrations/executor.py", line 79, in _create_project_state
        migration.mutate_state(state, preserve=False)
      File "/home/razia/.virtualenvs/web-dj2/lib/python3.6/site-packages/django/db/migrations/migration.py", line 85, in mutate_state
        operation.state_forwards(self.app_label, new_state)
      File "/home/razia/.virtualenvs/web-dj2/lib/python3.6/site-packages/django/db/migrations/operations/fields.py", line 144, in state_forwards
        delay = not old_field.is_relation
    AttributeError: 'NoneType' object has no attribute 'is_relation'

Answer 1

迁移有时需要一些人工干预。如果您正在单独执行一个项目，您可以宣布“迁移破产”，并在不丢失数据的情况下从零开始重新创建迁移，方法是运行新创建的带有-假冒伪劣的初始选项的迁移。

这里还有更多的细节，我建议先阅读一下：

https://docs.djangoproject.com/en/2.0/topics/migrations/#initial-migrations