I found the problem. I SHOULD INCLUDE URLS IN MAIN urls.py IN THE PROJECT
NOT IN ANOTHER URLS EXISTS IN INCLUDED APPS

Like this --> 
urlpatterns = [
    path('admin/', admin.site.urls),
    path('', include('paintshop.urls')),
    path('ckeditor/', include('ckeditor_uploader.urls')), <-- here it is.
]