Views RSS feeds have validation issues

Problem/Motivation

Summary

When creating an RSS feed display and submitting it for validation to the w3c validator, the latter complains about a recommendation that should be implemented (an atom:link tag should be inserted).

Steps to reproduce

1. Enable views & views_ui (7.x-3.x-dev)
2. Go to admin/structure/views/add, create a view with a feed display of type RSS, assign it a title and a path and make it accessible to anonymous users (see this screenshot)
3. Save the view
4. Go to http://validator.w3.org/feed/
5. Under 'Validate by URI' tab, enter the URL of the feed

Expected result

• The RSS feed validates without complaining

Actual result

• A message shows up saying it is a best practice to use an atom:link tag (see this screenshot)
• The RSS 2.0 spec seems to recommend the same

Proposed resolution

Patch suggested in #5 (this can be tested on https://simplytest.me/ for instance).
When validating the view with the patch, the W3C validator does not complain (see this screenshot).

Related Issues

• This problem occurs when using Drupal's core RSS feed #365498: Add missing atom:link with rel="self" to RSS feeds
• This problem does not occur when using views_rss

Original report by jvieille

I am trying to subscribe a LinkedIngroup to the rss feeds from a Drupal web site.
This feed is generated by my frontpage view.

No items are collected from linkedIn, and I am suspecting some strict validation control by LinkedIn
Feed validator says that the RSS feed is valid, but reports errors
http://validator.w3.org/feed/
the feed address is http://web2.see.asso.fr/rss.xml

- "description should not contain relative URL references"
- "Use of unknown namespace: http://drupal.org/group/og"
- "style attribute contains potentially dangerous content: white-space: pre;"
- "Invalid HTML: EOF in middle of construct"
- Missing atom:link with rel="self"

Thanks for help