verify: avoid shadowing two variables with a list comprehension

The variable names are clearly worse now, but since we're really just
transposing key and value I'm not too worried about the clarity loss.

mercurial/verify.py

@@ -425,7 +425,7 b' class verifier(object):'
 
             # cross-check
             if f in filenodes:
-                fns = [(lr, n) for n, lr in filenodes[f].iteritems()]
+                fns = [(v, k) for k, v in filenodes[f].iteritems()]
                 for lr, node in sorted(fns):
                     self.err(lr, _("manifest refers to unknown revision %s") %
                              short(node), f)