error: fetching feed 'com_ubuntu_filtered' - HTTP status 404 Not Found

I have this in the aggrgator logs:
```
[error] *** error: fetching feed 'com_ubuntu_filtered' - HTTP status 404 Not Found
```

The feed exists (https://ubuntu.com/blog/feed)...

But siftrss does not like it (https://siftrss.com/f/oq5vJZzdW3) and gives this:
```
Uh oh.
This feed appears to be too large to download.
Make your way back to the homepage and try again.
```