Hello. The following seems a little weird:

Python 3.3.2 (v3.3.2:d047928ae3f6, May 16 2013, 00:03:43) [MSC v.1600 32 bit (Intel)] on win32
>>> m = memoryview(b'123')
>>> list(m[::-1])
[51, 50, 49]
>>> list(reversed(m))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: object of type 'memoryview' has no len()
>>>

The attached patch allows `reversed` to be called with memoryviews and it could potentially fix issue18690.