anchor.diff:  
   -spec send_command(python_interpreter(), string(), [term()]) -> term().
   send_command(#python_interpreter{python_port = PythonPort} = PythonInterpreter, CmdTemplate, Args) ->
  +    Command = mzb_string:format(CmdTemplate, Args),
       port_command(PythonPort, io_lib:format("try:\n"
           "    mzbench._instruction_end(~s)\n"
           "except:\n"
           "    traceback.print_exc()\n"
           "    mzbench._instruction_failed(sys.exc_info())\n"
           "\n", 
  -        [io_lib:format(CmdTemplate, Args)])),
  +        [Command])),
       read_python_output(PythonInterpreter).
   
   -spec read_python_output(python_interpreter()) -> term().
  
positive.code:                             metrics_pipe_name   = MetricsPipeName, 
                              python_port         = PythonPort
                          }) ->
      port_command(PythonPort, "quit()\n"),
      wait_python_stop(PythonPort),
      close_fifo(MetricsPipeName, MetricsPipe).
  
  -spec wait_python_stop(port()) -> ok.
  
negative.code:             end,
              receive
                  {PythonPort, {exit_status, _Status}} ->
                      _ = (catch port_close(PythonPort)),
                      ok
              end;
          {PythonPort, {data, {eol, Line}}} ->
  