It seems the wsgiref package was copied from Python 2.* without any
modifications. There are already 3 issues about that but they only
describe a part of the problem so I decided to start a new one. The
issues was:

http://bugs.python.org/issue3348
http://bugs.python.org/issue3795
http://bugs.python.org/issue4522

The attached patch fix the problem with the following changes:

- Fixed headers handling in wsgiref/simple_server.py;

- Fixed encoding problems. Now WSGI applications must return iterable
with bytes but start_response() allow status and headers as bytes and as
strings. "wsgi.input" file-like now use BytesIO instead of StringIO;

- Fixed tests;

- Updated documentation examples;