Django: エラー解決法 TypeError: __init__() missing 1 required positional argument: ‘app_module’

Python 3.8.2、Django==3.0.5の環境で、python manage.py runserverを実行した際に下記のエラーが発生し、サーバーが起動しない事象が発生。

エラーメッセージ

vscode@d2a06e1c5d42:/workspace$ python manage.py runserver
Watching for file changes with StatReloader
Performing system checks...

System check identified no issues (0 silenced).
April 18, 2020 - 09:48:16
Django version 3.0.5, using settings 'crossk.settings'
Starting development server at 
Quit the server with CONTROL-C.
Exception in thread django-main-thread:
Traceback (most recent call last):
  File "/usr/local/lib/python3.8/threading.py", line 932, in _bootstrap_inner
    self.run()
  File "/usr/local/lib/python3.8/threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File "/home/vscode/.local/lib/python3.8/site-packages/django/utils/autoreload.py", line 53, in wrapper
    fn(*args, **kwargs)
  File "/home/vscode/.local/lib/python3.8/site-packages/django/core/management/commands/runserver.py", line 137, in inner_run
    handler = self.get_handler(*args, **options)
  File "/home/vscode/.local/lib/python3.8/site-packages/django/contrib/staticfiles/management/commands/runserver.py", line 27, in get_handler
    handler = super().get_handler(*args, **options)
  File "/home/vscode/.local/lib/python3.8/site-packages/django/core/management/commands/runserver.py", line 64, in get_handler
    return get_internal_wsgi_application()
  File "/home/vscode/.local/lib/python3.8/site-packages/django/core/servers/basehttp.py", line 45, in get_internal_wsgi_application
    return import_string(app_path)
  File "/home/vscode/.local/lib/python3.8/site-packages/django/utils/module_loading.py", line 17, in import_string
    module = import_module(module_path)
  File "/usr/local/lib/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 783, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/workspace/crossk/wsgi.py", line 16, in <module>
    application = get_wsgi_application()
  File "/home/vscode/.local/lib/python3.8/site-packages/django/core/wsgi.py", line 13, in get_wsgi_application
    return WSGIHandler()
  File "/home/vscode/.local/lib/python3.8/site-packages/django/core/handlers/wsgi.py", line 127, in __init__
    self.load_middleware()
  File "/home/vscode/.local/lib/python3.8/site-packages/django/core/handlers/base.py", line 37, in load_middleware
    mw_instance = middleware(handler)
TypeError: __init__() missing 1 required positional argument: 'app_module'

原因

settings.pyのINSTALLED_APPSリストに作成したapp名を記載するところ、誤って、MIDDLEWAREリストに記載していた為。

解決法

MIDDLEWAREリストに記載しているapp名を削除し、INSTALLED_APPSリストにapp名を記載すれば良い。

参考サイト