correct the argument to warn function

IPython/core/displayhook.py

@@ -45,7 +45,7 b' class DisplayHook(Configurable):'
             self.do_full_cache = 0
             cache_size = 0
             warn('caching was disabled (min value for cache size is %s).' %
-                 cache_size_min,level=3)
+                 cache_size_min,stacklevel=3)
         else:
             self.do_full_cache = 1