refs #9438 Better diagnostics

During IDF changes, it was found difficult to understand what is going wrong when monitor number is specified incorrectly. This change should help to address similar problem in a future.

Code/Mantid/scripts/Inelastic/DirectEnergyConversion.py

@@ -402,7 +402,7 @@ def _do_mono_SNS(self, data_ws, monitor_ws, result_name, ei_guess,
 
             ConvertFromDistribution(Workspace=result_name)  
 
-        # Normalise using the chosen method
+        # Normalize using the chosen method
         # This should be done as soon as possible after loading and usually happens at diag. Here just in case if diag was bypassed
         self.normalise(mtd[result_name], result_name, self.normalise_method, range_offset=bin_offset)
 
@@ -445,7 +445,7 @@ def _do_mono_ISIS(self, data_ws, monitor_ws, result_name, ei_guess,
                                      WorkspaceIndexList= '',Mode= 'Mean',SkipMonitors='1')
 
 
-        # Normalise using the chosen method+group
+        # Normalize using the chosen method+group
         # : This really should be done as soon as possible after loading
         self.normalise(mtd[result_name], result_name, self.normalise_method, range_offset=bin_offset)
 
@@ -472,7 +472,7 @@ def _do_mono(self, data_ws, monitor_ws, result_name, ei_guess,
                  white_run=None, map_file=None, spectra_masks=None, Tzero=None):
         """
         Convert units of a given workspace to deltaE, including possible 
-        normalisation to a white-beam vanadium run.
+        normalization to a white-beam vanadium run.
         """
         if (self.__facility == "SNS"):
            self._do_mono_SNS(data_ws,monitor_ws,result_name,ei_guess,
@@ -610,13 +610,17 @@ def get_ei(self, input_ws, resultws_name, ei_guess):
         if type(monitor_ws) is str:
             monitor_ws = mtd[monitor_ws]
         try: 
-            # check if the spectra with correspondent number is present in the worksace
+            # check if the spectra with correspondent number is present in the workspace
             nsp = monitor_ws.getIndexFromSpectrumNumber(int(self.ei_mon_spectra[0]));
-        except:
+        except RuntimeError as err:
             monitors_from_separate_ws = True
             mon_ws = monitor_ws.getName()+'_monitors'
-            monitor_ws = mtd[mon_ws];
-        #-------------------------------------------------------------
+            try:
+                monitor_ws = mtd[mon_ws];
+            except:
+                print "**** ERROR while attempting to get spectra {0} from workspace: {1}, error: {2} ".format(self.ei_mon_spectra[0],monitor_ws.getName(), err)
+                raise
+        #------------------------------------------------
 
         # Calculate the incident energy
         ei,mon1_peak,mon1_index,tzero = \