Need the ability to hook existing standard library modules

[Mystic-Mirage]

Today I tried to backport datetime module from Python 3.3 (there are new timezone class and datetime.timestamp method).

I placed new datetime.py into future/standard_library/ and added 'future.standard_library.datetime': 'datetime' to RENAMES but existing hook algorithm prevents module overriding if it is already exists in sys.modules.

So how it can be done?