I tried a few online python 3 interpreters.

These give the same exception:

http://www.learnpython.org/en/Hello%2C_World%21
http://rextester.com/l/python3_online_compiler
http://ideone.com/pIMilt
http://www.tutorialspoint.com/execute_python3_online.php

And this one worked:

https://repl.it/languages/python3

the example i tried was:

from wsgiref.simple_server import make_server, demo_app
with make_server('', 8000, demo_app) as httpd:
    print("Serving HTTP on port 8000...")
    httpd.serve_forever()

My Python installation is a default x64 installation. No changes were made during installation, except installation path, which has no spaces in it. I have no third part modules installed which could interfer. I have also a Python 2.7 installed but it is not on my path.