Writer.php

public function format_message(array $message, $format = "time --- level: body in file:line")
    {
        $message['time'] = Date::formatted_time('@'.$message['time'], Log_Writer::$timestamp, Log_Writer::$timezone, TRUE);
        $message['level'] = $this->_log_levels[$message['level']];

        $string = strtr($format, array_filter($message, 'is_scalar'));

        if (isset($message['additional']['exception']))
        {
            // Re-use as much as possible, just resetting the body to the trace
            $message['body'] = $message['additional']['exception']->getTraceAsString();
            $message['level'] = $this->_log_levels[Log_Writer::$strace_level];

            $string .= PHP_EOL.strtr($format, array_filter($message, 'is_scalar'));
        }

        return $string;
    }