Extensions code blocks not displaying properly (data-gb-custom-block)

[gdahl-ivy]

Issue description

Some code blocks on the extensions pages are not being displayed properly. There is no syntax highlighting (all the text is red) and the {% ... %} blocks are replaced with <div data-gb-custom-block data-tag="url" data-0='post_detail'></div> or similar. This makes it difficult to follow the tutorial without breaking something or guessing incorrectly what the tag text is supposed to be.

Example

These are the two affected pages:
Homework: add more to your website!
Homework: create comment model

Language

Not language-specific

Operating system

Windows 10, Chrome v104.0