implemented a signature-preserving contexmanager decorator. Fixed a bug
with the signature f(**kw) in Python 3 and fixed a couple of doctests
broken by Python 3.3.
3.3.3 Fixed a bug with kwonlyargs for Python 3
The ``decorator'' module aims to simplify the usage of decorators
in Python code for the average programmer and to popularize decorators
by showing various non-trivial examples.