This issue is part of #1333730: [Meta] PHP DOM (libxml2) only understands XHTML4, misinterprets HTML5, but D8 must cope with HTML5.
The Drupal\system\Tests\Theme\FunctionsTest needs to be upgraded to HTML5.
Beta phase evaluation
| Issue priority | Major because the testing system needs HTML5 support to test HTML5 code. |
|---|---|
| Prioritized changes | The main goal of this issue is a bugfix to for HTML5 support, which is part of the Drupal 8 product. |
Commit credits
Please give commit credits to all who have worked on the parent issue (#1333730: [Meta] PHP DOM (libxml2) only understands XHTML4, misinterprets HTML5, but D8 must cope with HTML5).