I moved this blog to a new blog software and had lost the ability to build custom feeds on tags. This should at least work now for the Python tag again and so your feed readers should be able to load Python feed again. Let me know if this is not working.
The IDs of posts in that feed are probably not the same as in the static site generator I used before, so your feed reader might show some old posts as unread, although you have read them already.