Prevent page crash when using default comparer on Global Status page

[tnfchris]

Summary

When LNT was still Python 2 the default comparer was able to handle None values with <, however Python 3 doesn't support this. As a result after the Python 3 upgrade the Global Status page crashes when sorting any values with None in them in the second column.

I believe this happens when there is no regression detected so this is a valid state.

There are two ways to handle this, either filter out the None values or sort them all the same. I have choosen the second approach since I believe that is what Python 2 did.

[thopre]

I can reproduce the issue and the patch LGTM. Thanks!

[thopre]

Actually, could you try adding a testcase? There's a test for global_status in tests/server/ui/V4Pages.py

[thopre]

In D85422#2199400, @thopre wrote:

Actually, could you try adding a testcase? There's a test for global_status in tests/server/ui/V4Pages.py

I've created a test for it in D87235. I'll approve this once the test is approved by Chris.

[thopre]

In D85422#2259230, @thopre wrote:

In D85422#2199400, @thopre wrote:

Actually, could you try adding a testcase? There's a test for global_status in tests/server/ui/V4Pages.py

I've created a test for it in D87235. I'll approve this once the test is approved by Chris.

As promised, approved. I'll commit it on your behalf.

[thopre]

Landed as 83c975ef66db04615077d6a6f819f42e90e8fa67

lnt/server/ui/views.py

for i, (test_id, test_name) in enumerate(reported_tests):
         # Compute the worst cell value.
         if len(row) > 2:
             row[1] = max(cr.pct_delta
                          for cr, _ in row[2:])
 
         test_table.append(row)
 
     # Order the table by worst regression.
-    test_table.sort(key=lambda row: row[1], reverse=True)
+    test_table.sort(key=lambda row: 0 if row[1] is None else row[1], reverse=True)
 
     return render_template("v4_global_status.html",
                            tests=test_table,
                            machines=recent_machines,
                            fields=metric_fields,
                            selected_field=field,
                            selected_revision=revision,
                            **ts_data(ts))