Fill in any missing data columns when printing data tables.

We only combine data tables if they contain the same data to be tested.
However, if a column is missing but is not included in the tests, this
led to an exception when we attempted to print out data not present in
one or other of the test and benchmark.

Instead, in such cases, fill in the data with 'n/a' entries.

Reported by: Nick Blunt.

lib/testcode2/util.py

@@ -157,6 +157,22 @@ def wrap_list_strings(word_list, width):
 
 def pretty_print_table(labels, dicts):
     '''Print data in dictionaries of identical size in a tabular format.'''
+    # Fill in the dicts with missing data.
+    # This can be hit if the missing data fields are ignored...
+    for dict1 in dicts:
+        for key in dict1.keys():
+            if type(dict1[key]) is tuple or type(dict1[key]) is list:
+                nitems = len(dict1[key])
+                val = ('n/a',)*nitems
+                iterable = True
+            else:
+                val = 'n/a'
+                iterable = False
+            for dict2 in dicts:
+                if key not in dict2:
+                    dict2[key] = val
+                elif iterable and nitems != len(dict2[key]):
+                    dict2[key] += nitems - len(dict2[key])
     # Loop through all elements in order to calculate the field width.
     # Create header line as we go.
     fmt = dict(_tc_label='%%-%is' % (max(len(str(label)) for label in labels)))