Scan scss from string and return nodes.

def scan(src):
        """ Scan scss from string and return nodes.
        """
        assert isinstance(src, (unicode_, bytes_))
        try:
            nodes = STYLESHEET.parseString(src, parseAll=True)
            return nodes
        except ParseBaseException:
            err = sys.exc_info()[1]
            print(err.line, file=sys.stderr)
            print(" " * (err.column - 1) + "^", file=sys.stderr)
            print(err, file=sys.stderr)
            sys.exit(1)