log (RFilter::DeliveryAgent)

    # File lib/rfilter/delivery_agent.rb, line 219
        def log(level, str)
          if level <= 0 and @logfile.nil?
            raise LoggingError, "failed to log high priority message: #{str}"
          end
          return if @logfile.nil? or level > @logging_level
          begin
            @logfile.flock(File::LOCK_EX)
            @logfile.print(Time.now.strftime("%Y/%m/%d %H:%M:%S "))
            @logfile.print(sprintf("%05d: ", Process.pid))
            @logfile.puts(str)
            @logfile.flush
            @logfile.flock(File::LOCK_UN)
          rescue
            # FIXME: this isn't tested
            raise LoggingError.new("failed to log message: #{str}", $!)
          end
        end