anchor.diff:      _stdoutStream.onLine = _readStdout(_stdoutStream, _testStdout);
       _stderrStream.onLine = _readStderr(_stderrStream, _testStderr);
       _process.onExit = _exitHandler;
  +    _process.onError = (e) {
  +      print("Error starting process:");
  +      print("  Command: $_executable ${Strings.join(_batchArguments, ' ')}");
  +      print("  Error: $e");
  +    };
       _process.onStart = then;
     }
   }
  
positive.code:   bool get hasTimedOut();
  
    bool get didFail();
    
    bool requestRetry;
  
    Duration get time();
  
negative.code:       Process p = new Process.start(cmd, arg);
        final StringInputStream stdoutStringStream =
            new StringInputStream(p.stdout);
        p.onError = (e) {
          print("Error starting process:");
          print("  Command: $cmd ${Strings.join(arg, ' ')}");
          print("  Error: $e");
        };
        stdoutStringStream.onLine = () {
          var line = stdoutStringStream.readLine();
          while (null != line) {
  