anchor.diff:    var styleSheet = parse(css, errors: errors);
   
     if (errors.isNotEmpty) {
  -    logger.warning('Errors parsing CSS:\n${errors.join('\n')}');
  +    logger.severe('Errors parsing CSS:\n${errors.join('\n')}');
     }
   
     var shadowTransformer = useLegacyEncapsulation
  
positive.code: 
    var selectorGroup = parseSelectorGroupFrom(declaration);
    if (selectorGroup == null) {
      logger.warning(declaration.expression.span.message('Not a valid selector'));
      return null;
    }
  
  
negative.code:     {bool remove: false}) {
    var declaration = getDeclaration(declarationGroup, propertyName);
    if (declaration == null) {
      logger.severe(
          declarationGroup.span.message("Expected property '$propertyName'"));
      return null;
    }
  