Message1272

test_hmac and test_pep247 fail because of problems with the SHA module.

* SHA and MD5 objects lack a .digest_size attribute.

* Successive calls to digest() return different values.

* For digest(), the byte array is converted to a string using the default encoding, which produces weird results if it's UTF-8.  It should hardwire using ISO-8859-1, because we want a 1-to-1 mapping of characters.

The attached patch fixes test_pep247.  test_hmac still fails; I'm still looking into the problem.