Read pickles in pure binary mode.

In 4ab240d53a we changed to pickle protocol 2 that introduces more
binary data, so trying to read back those pickles in 'U' mode will
cause strange unpickling errors.

IPython/utils/pickleshare.py

@@ -67,7 +67,7 b' class PickleShareDB(collections.MutableMapping):'
             return self.cache[fil][0]
         try:
             # The cached item has expired, need to read
-            obj = pickle.loads(fil.open("rbU").read())
+            obj = pickle.loads(fil.open("rb").read())
         except:
             raise KeyError(key)