Apply undo list in reverse order; in rare cases with hints with overlapping virtual packages provided by different sources, this can make a difference.

britney.py

@@ -2412,6 +2412,7 @@ class Britney(object):
         else:
             self.output_write("FAILED\n")
             if not lundo: return
+            lundo.reverse()
 
             self.undo_changes(lundo, self.systems, self.sources, self.binaries)