Build/Test Tools: Ensure assertEqualHTML fallback render can be reached.

`assertEqualHTML` catches `Exception`s and attempts to re-parse the HTML with the `Dom\HtmlDocument` class. Ensure that the fallback render is reachable by throwing `Exception` instead of `Error` in the tree builder function.

Developed in #9273.

Follow-up to [60295].

Props jonsurrell, bernhard-reiter, dmsnell.
Fixes #63527.


git-svn-id: https://develop.svn.wordpress.org/trunk@60707 602fd350-edb4-49c9-b593-d223f7449a82

Author: sirreal

tests/phpunit/includes/build-visual-html-tree.php

@@ -40,7 +40,7 @@
  *
  * @since 6.9.0
  *
- * @throws WP_HTML_Unsupported_Exception|Error If the markup could not be parsed.
+ * @throws WP_HTML_Unsupported_Exception|Exception If the markup could not be parsed.
  *
  * @param string      $html             Given test HTML.
  * @param string|null $fragment_context Context element in which to parse HTML, such as BODY or SVG.
@@ -51,7 +51,7 @@ function build_visual_html_tree( string $html, ?string $fragment_context ): stri
 		? WP_HTML_Processor::create_fragment( $html, $fragment_context )
 		: WP_HTML_Processor::create_full_parser( $html );
 	if ( null === $processor ) {
-		throw new Error( 'Could not create a parser.' );
+		throw new Exception( 'Could not create a parser.' );
 	}
 	$tree_indent = '  ';
 
@@ -280,7 +280,7 @@ static function ( $a, $b ) {
 			default:
 				// phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_var_export
 				$serialized_token_type = var_export( $processor->get_token_type(), true );
-				throw new Error( "Unhandled token type for tree construction: {$serialized_token_type}" );
+				throw new Exception( "Unhandled token type for tree construction: {$serialized_token_type}" );
 		}
 	}
 
@@ -289,11 +289,11 @@ static function ( $a, $b ) {
 	}
 
 	if ( null !== $processor->get_last_error() ) {
-		throw new Error( "Parser error: {$processor->get_last_error()}" );
+		throw new Exception( "Parser error: {$processor->get_last_error()}" );
 	}
 
 	if ( $processor->paused_at_incomplete_token() ) {
-		throw new Error( 'Paused at incomplete token.' );
+		throw new Exception( 'Paused at incomplete token.' );
 	}
 
 	if ( '' !== $text_node ) {