def get_assembler assembler
      ret = @assemblers.find do |a|
        a.name == assembler ||
        a.shortname == assembler
      end
      raise "couldn't find assembler #{assembler}" if ret.nil?
      ret
    end
def get_assembler assembler
      ret = @assemblers.find do |a|
        a.name == assembler ||
        a.shortname == assembler
      end
      raise "couldn't find assembler #{assembler}" if ret.nil?
      ret
    end
Given the name of an assembler, get the loaded assembler
 ready for optimisation.

 @param assembler [String] assembler name or shortname
 @return [Biopsy::Target] the loaded assembler