fix trace name handling in VNA_dummy

Python_script/VNA_dummy.py

@@ -71,7 +71,7 @@ class VnaDummy:
         return self.simulated_traces
 
     def create_new_trace(self, name, parameter):
-        self.simulated_traces.append((name, parameter))
+        self.simulated_traces.append(name)
 
     def set_trace_measurements(self, trace, measurement):
         pass
@@ -94,8 +94,8 @@ class VnaDummy:
         return '1'
     
     def get_measurement_string(self, trace, result_format):
-
-        self.simulated_traces = trace
+        if trace not in self.simulated_traces:
+            raise Exception('trace '+trace+' is not known to VNA dummy!')
         self.result_format = result_format
 
         phase_radian = self.simulated_phase / 180. * math.pi