django.core.exceptions.ImproperlyConfigured: Specifying a namespace in include() without providing a

django.core.exceptions.ImproperlyConfigured: Specifying a namespace in include() without providing an app_name is not supported. Set the app_name attribute in the included module, or pass a 2-tuple containing the list of patterns and app_name instead.

在运行Django项目时报此异常，查看代码发现主应用的urlpatterns 如下写法：

urlpatterns = [
    path('admin/', admin.site.urls),
    path('test/', include('djchild.urls', namespace="djchild"))
]

将子应用的urls.py和namespace放在一个元组里进行替换即可解决，即：

urlpatterns = [
    path('admin/', admin.site.urls),
    path('test/', include(('djchild.urls', "djchild")))
]