Deprecation: legacy nested tags

The nested tag syntax has changed to use the new <@tag> attribute tag syntax. Previously, the syntax was <parent-tag-name:nested-tag-name>.

❗️ If you’re using XML namespaces, you’re probably seeing this error. See Issue #1297 for more info.

The older nested tag syntax:

<my-tag>
  <my-tag:nested-tag>Content</my-tag:nested-tag>
</my-tag>

…now looks like this with tag attributes:

<my-tag>
  <@nested-tag>Content</@nested-tag>
</my-tag>