Fixed Flake8/McCabe violations

The code is imho not really better, but it reaches a score lower then 10 McCabe analysis.

I also renamed the `rss.pt` to `rss.pt.xml` this prevents zptlint from validating this file.
It's not possible, since `<link>...</link>` is used for RSS2 
Valid in pt is only `<link />` without any content.