Fix measurement file path.

- was introduced in 538a31d5
- solves #11216

Python_script/climate-lab-gui.py

@@ -103,7 +103,8 @@ class TestStandMainWindow(QMainWindow):
 
             elif self.measurementFileButton.isChecked():
                 try:
-                    n_measurements = meas.perform_measurements(self.measurementFile.text())
+                    n_measurements = meas.perform_measurements(os.path.join(self.start_dir,
+                                                                            self.measurementFile.text()))
                     prototype.plot_output(output_basename, range(n_measurements), True, output_basename)
                 except FileNotFoundError as e:
                     QtWidgets.QMessageBox.warning(self, 'Warning', str(e))