我正在按照this tutorial学习如何使用Django。
但是，每次尝试使用管理站点来编辑数据库时，我都会遇到OperationalError异常。
跟踪：
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\db\backends\utils.py" in _execute
85. return self.cursor.execute(sql, params)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\db\backends\sqlite3\base.py" in execute
296. return Database.Cursor.execute(self, query, params)
The above exception (no such table: main.auth_user__old) was the direct cause of the following exception:
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\core\handlers\exception.py" in inner
34. response = get_response(request)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\core\handlers\base.py" in _get_response
126. response = self.process_exception_by_middleware(e, request)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\core\handlers\base.py" in _get_response
124. response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\contrib\admin\options.py" in wrapper
604. return self.admin_site.admin_view(view)(*args, **kwargs)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\utils\decorators.py" in _wrapped_view
142. response = view_func(request, *args, **kwargs)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\views\decorators\cache.py" in _wrapped_view_func
44. response = view_func(request, *args, **kwargs)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\contrib\admin\sites.py" in inner
223. return view(request, *args, **kwargs)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\contrib\admin\options.py" in change_view
1639. return self.changeform_view(request, object_id, form_url, extra_context)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\utils\decorators.py" in _wrapper
45. return bound_method(*args, **kwargs)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\utils\decorators.py" in _wrapped_view
142. response = view_func(request, *args, **kwargs)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\contrib\admin\options.py" in changeform_view
1525. return self._changeform_view(request, object_id, form_url, extra_context)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\contrib\admin\options.py" in _changeform_view
1571. self.log_change(request, new_object, change_message)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\contrib\admin\options.py" in log_change
826. change_message=message,
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\contrib\admin\models.py" in log_action
35. change_message=change_message,
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\db\models\manager.py" in manager_method
82. return getattr(self.get_queryset(), name)(*args, **kwargs)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\db\models\query.py" in create
413. obj.save(force_insert=True, using=self.db)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\db\models\base.py" in save
718. force_update=force_update, update_fields=update_fields)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\db\models\base.py" in save_base
748. updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\db\models\base.py" in _save_table
831. result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\db\models\base.py" in _do_insert
869. using=using, raw=raw)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\db\models\manager.py" in manager_method
82. return getattr(self.get_queryset(), name)(*args, **kwargs)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\db\models\query.py" in _insert
1136. return query.get_compiler(using=using).execute_sql(return_id)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\db\models\sql\compiler.py" in execute_sql
1289. cursor.execute(sql, params)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\db\backends\utils.py" in execute
100. return super().execute(sql, params)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\db\backends\utils.py" in execute
68. return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\db\backends\utils.py" in _execute_with_wrappers
77. return executor(sql, params, many, context)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\db\backends\utils.py" in _execute
85. return self.cursor.execute(sql, params)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\db\utils.py" in __exit__
89. raise dj_exc_value.with_traceback(traceback) from exc_value
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\db\backends\utils.py" in _execute
85. return self.cursor.execute(sql, params)
File "C:\Users\Zhang\AppData\Local\Continuum\anaconda3\lib\site-packages\django\db\backends\sqlite3\base.py" in execute
296. return Database.Cursor.execute(self, query, params)
Exception Type: OperationalError at /admin/auth/user/2/change/
Exception Value: no such table: main.auth_user__old
我在理解错误消息时遇到了麻烦，因此我深入研究代码以了解其含义。
在路径utils.py中的文件C:\Users\Zhang\AppData\Local\Continuum\anaconda3\Lib\site-packages\django\db中，我发现异常是作为空类实现的。
具体来说，
class Error(Exception):
pass
class InterfaceError(Error):
pass
class DatabaseError(Error):
pass
class DataError(DatabaseError):
pass
class OperationalError(DatabaseError):
pass
class IntegrityError(DatabaseError):
pass
class InternalError(DatabaseError):
pass
class ProgrammingError(DatabaseError):
pass
class NotSupportedError(DatabaseError):
pass
我要问的主要问题：这样做的目的是什么？ Django为什么要留下一堆扩展Exception的空类？
此外，为什么Django有自己的sqlite3文件夹？据我了解，sqlite3已包含在标准的Python3安装中，因此是否不必拥有自己的sqlite3库？