def open(io)
      begin
        @@logger = Logger.new(io, *@@options)
      rescue IOError => e
        @@logger = Logger.new($stderr)
        $stderr.puts "Cannot open log file: #{e.message}"
      end
      @@logger.level = @@level
      @@logger.formatter = @@formatter
    end
def open(io)
      begin
        @@logger = Logger.new(io, *@@options)
      rescue IOError => e
        @@logger = Logger.new($stderr)
        $stderr.puts "Cannot open log file: #{e.message}"
      end
      @@logger.level = @@level
      @@logger.formatter = @@formatter
    end
Redirect all log messages to the given IO.
 @param io [IO] Output file descriptor