'Process an empty line in a block scalar.'

def parse_block_scalar_empty_line(indent_token_class, content_token_class):

    def callback(lexer, match, context):
        text = match.group()
        if ((context.block_scalar_indent is None) or (len(text) <= context.block_scalar_indent)):
            if text:
                (yield (match.start(), indent_token_class, text))
        else:
            indentation = text[:context.block_scalar_indent]
            content = text[context.block_scalar_indent:]
            (yield (match.start(), indent_token_class, indentation))
            (yield ((match.start() + context.block_scalar_indent), content_token_class, content))
        context.pos = match.end()
    return callback
