PEP8 formatting in Bio.HotRand; Use increment operator
The Bio.HotRand.hex_convert function was removed 3 years ago
Fix Bio.HotRand under Python 3.

Until recently the (online) test for Bio.HotRand was
silently passing without actually testing the code,
so we never noticed it was broken under Python 3 :(

In anycase, this module has been deprecated.