Reverse for 'ckeditor_upload' not found. 'ckeditor_upload' is not a valid view function or pattern name.
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.
]