py3: convert dict.items() to list explicitly

On python 3, dict.items() returns a dict_items object which cannot be sorted.

Differential Revision: https://phab.mercurial-scm.org/D2415

hgext/churn.py

@@ -171,7 +171,7 b' def churn(ui, repo, *pats, **opts):'
                     ui.warn(_("skipping malformed alias: %s\n") % l)
                 continue
 
-    rate = countrate(ui, repo, amap, *pats, **opts).items()
+    rate = list(countrate(ui, repo, amap, *pats, **opts).items())
     if not rate:
         return