fix hello.py (ALL strings passed to or from the server must be of type
str or bytes)

from PEP 3333:
HTTP does not directly support Unicode, and neither does this interface. All encoding/decoding must be handled by the application; all strings passed to or from the server must be of type str or bytes, never unicode. The result of using a unicode object where a string object is required, is undefined.
Note also that strings passed to start_response() as a status or as response headers must follow RFC 2616 with respect to encoding. That is, they must either be ISO-8859-1 characters, or use RFC 2047 MIME encoding.