def backtrace(exc, level_meth = :error)
      return unless show_backtraces
      send(level_meth, "#{exc.class.class_name}: #{exc.message}")
      send(level_meth, "Stack trace:" +
        exc.backtrace[0..5].map {|x| "\n\t#{x}" }.join + "\n")
    end
def backtrace(exc, level_meth = :error)
      return unless show_backtraces
      send(level_meth, "#{exc.class.class_name}: #{exc.message}")
      send(level_meth, "Stack trace:" +
        exc.backtrace[0..5].map {|x| "\n\t#{x}" }.join + "\n")
    end
Prints the backtrace +exc+ to the logger as error data.

 @param [Array<String>] exc the backtrace list
 @param [Symbol] level_meth the level to log backtrace at
 @return [void]