Django报错求助：ContentType未声明app_label且不在INSTALLED_APPS中

我正在为客户调试一个NGINX/Django/UWSGI应用，故障超出预期，已经调试、重写代码30余小时，现在碰到无法解决的障碍，报错信息如下：

[pid: 336873|app: 0|req: 1/1] 198.11.30.68 () {46 vars in 1070 bytes} [Mon Dec  5 10:04:42 2022] GET / => generated 0 bytes in 393 msecs (HTTP/1.1 500) 0 headers in 0 bytes (0 switches on core 0)
announcing my loyalty to the Emperor...
Traceback (most recent call last):
  File "/home/django/django_venv/django_site/wsgi.py", line 26, in application
    get_wsgi_application();
  File "/home/django/django_venv/lib64/python3.6/site-packages/django/core/wsgi.py", line 12, in get_wsgi_application
    WSGIHandler();
  File "/home/django/django_venv/lib64/python3.6/site-packages/django/core/handlers/wsgi.py", line 127, in __init__
    self.load_middleware()
  File "/home/django/django_venv/lib64/python3.6/site-packages/django/core/handlers/base.py", line 40, in load_middleware
    middleware = import_string(middleware_path)
  File "/home/django/django_venv/lib64/python3.6/site-packages/django/utils/module_loading.py", line 17, in import_string
    module = import_module(module_path)
  File "/usr/lib64/python3.6/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 994, in _gcd_import
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 678, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/home/django/django_venv/lib64/python3.6/site-packages/django/contrib/auth/middleware.py", line 3, in <module>
    from django.contrib.auth.backends import RemoteUserBackend
  File "/home/django/django_venv/lib64/python3.6/site-packages/django/contrib/auth/backends.py", line 2, in <module>
    from django.contrib.auth.models import Permission
  File "/home/django/django_venv/lib64/python3.6/site-packages/django/contrib/auth/models.py", line 5, in <module>
    from django.contrib.contenttypes.models import ContentType
  File "/home/django/django_venv/lib64/python3.6/site-packages/django/contrib/contenttypes/models.py", line 133, in <module>
    class ContentType(models.Model):
  File "/home/django/django_venv/lib64/python3.6/site-packages/django/db/models/base.py", line 116, in __new__
    "INSTALLED_APPS." % (module, name)
RuntimeError: Model class django.contrib.contenttypes.models.ContentType doesn't declare an explicit app_label and isn't in an application in INSTALLED_APPS.
[pid: 336874|app: 0|req: 1/2] 198.11.30.68 () {46 vars in 1049 bytes} [Mon Dec  5 10:04:42 2022] GET /favicon.ico => generated 0 bytes in 393 msecs (HTTP/1.1 500) 0 headers in 0 bytes (0 switches on core 0)
announcing my loyalty to the Emperor...

我的settings.py配置如下：

import django.utils
from pathlib import Path
import six
import localsettings as secret
import urls
import sys
import os
import django
django.setup()
# Quick-start development settings - unsuitable for production
# See https://docs.djangoproject.com/en/3.2/howto/deployment/checklist/

# SECURITY WARNING: keep the secret key used in production secret!
SECRET_KEY = <removed for privacy>

# SECURITY WARNING: don't run with debug turned on in production!
DEBUG = True

ALLOWED_HOSTS = [<removed for privacy>]
BASE_DIR = Path(__file__).resolve().parent.parent

# Application definition

INSTALLED_APPS = [
    'django.contrib.contenttypes',
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.sites',
    'django.contrib.sessions',
    'django.contrib.messages',
    'wsgi.application',
    'acknowledgments.apps.AcknowledgmentsConfig',
    'data_sources.apps.DataSourcesConfig',
    'home.apps.HomeConfig',
    'igv.apps.IgvConfig',
    'organisms.apps.OrganismsConfig',
    'samples.apps.SamplesConfig',
    'search.apps.SearchConfig',
    'summary.apps.SummaryConfig',
    ]
#import django.contrib.contenttypes.models.ContentType
MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
]

ROOT_URLCONF = 'urls'
SITE_ID = 1
TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [os.path.join(BASE_DIR, 'django_site.templates')],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]

WSGI_APPLICATION = "wsgi.application"


# Database
# https://docs.djangoproject.com/en/3.2/ref/settings/#databases


DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': secret.db_name,
        'USER': secret.db_user,
        'PASSWORD': secret.db_token,
        'HOST': secret.db_host,
        }
    }



# Password validation
# https://docs.djangoproject.com/en/3.2/ref/settings/#auth-password-validators

AUTH_PASSWORD_VALIDATORS = [
    {
        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
    },
]


# Internationalization
# https://docs.djangoproject.com/en/3.2/topics/i18n/

LANGUAGE_CODE = 'en-us'

TIME_ZONE = '<removed for privacy>'

USE_I18N = True

USE_L10N = True

USE_TZ = True


# Static files (CSS, JavaScript, Images)
# https://docs.djangoproject.com/en/3.2/howto/static-files/
STATIC_ROOT = os.path.join(BASE_DIR, "static/admin")
STATIC_URL ="static/admin/"

# Default primary key field type
# https://docs.djangoproject.com/en/3.2/ref/settings/#default-auto-field

DEFAULT_AUTO_FIELD = 'django.db.models.BigAutoField'

1. 清理INSTALLED_APPS中的无效项 #

INSTALLED_APPS列表里的'wsgi.application'不是合法的Django应用，直接删除该行。WSGI_APPLICATION已经在配置文件下方单独设置，无需放入应用列表。

修改后的INSTALLED_APPS：

INSTALLED_APPS = [
    'django.contrib.contenttypes',
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.sites',
    'django.contrib.sessions',
    'django.contrib.messages',
    'acknowledgments.apps.AcknowledgmentsConfig',
    'data_sources.apps.DataSourcesConfig',
    'home.apps.HomeConfig',
    'igv.apps.IgvConfig',
    'organisms.apps.OrganismsConfig',
    'samples.apps.SamplesConfig',
    'search.apps.SearchConfig',
    'summary.apps.SummaryConfig',
]

2. 删除提前调用的django.setup() #

settings.py开头的django.setup()属于错误调用，Django启动时会自动完成初始化流程，手动提前调用会打乱应用加载顺序，引发ContentType相关错误。删除以下两行：

import django
django.setup()

3. 移除不必要的导入 #

import urls这行导入没有实际作用，还可能导致循环导入问题，建议删除。

4. 验证配置并重启服务 #

修改完成后，运行以下命令检查配置合法性：

python manage.py check

如果无报错，重启UWSGI和NGINX服务即可。

内容的提问来源于stack exchange，提问作者Alex Noel