Fix error handling

Author: tvdijen

src/SchemaValidatableElementTrait.php

@@ -13,6 +13,8 @@
 use function defined;
 use function file_exists;
 use function implode;
+use function libxml_clear_errors;
+use function libxml_use_internal_errors;
 use function libxml_get_errors;
 use function sprintf;
 use function trim;
@@ -32,6 +34,9 @@ trait SchemaValidatableElementTrait
      */
     public static function schemaValidate(DOMDocument $document): DOMDocument
     {
+        $internalErrors = libxml_use_internal_errors(true);
+        libxml_clear_errors();
+
         $schemaFile = self::getSchemaFile();
         // Must suppress the warnings here in order to throw them as an error below.
         $result = @$document->schemaValidate($schemaFile);
@@ -48,6 +53,9 @@ public static function schemaValidate(DOMDocument $document): DOMDocument
             ));
         }
 
+        libxml_use_internal_errors($internalErrors);
+        libxml_clear_errors();
+
         return $document;
     }