With python2.6, reloading extension modules does not always leak memory:

Python 2.6b2+ (trunk, Aug 19 2008, 23:45:24) [MSC v.1500 32 bit (Intel)]
on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
[34467 refs]
>>> import audioop; del sys.modules['audioop']
[34677 refs]
>>> import audioop; del sys.modules['audioop']
[34677 refs]

But with 3.0, reloading audioop leaks 60 references every time (seen in
test_unittest):

Python 3.0b3+ (py3k, Aug 24 2008, 21:56:40) [MSC v.1500 32 bit (Intel)]
on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
[42018 refs]
>>> import audioop; del sys.modules['audioop']
[42257 refs]
>>> import audioop; del sys.modules['audioop']
[42317 refs]
>>> import audioop; del sys.modules['audioop']
[42377 refs]
>>> import audioop; del sys.modules['audioop']
[42437 refs]
>>> import audioop; del sys.modules['audioop']
[42497 refs]

OK, many things cannot be reinitialized for C-written modules (static
variables &co), this is not the case for audioop. Furthermore, I thought
that the new module API was to support proper cleanup of modules

The fix is actually simple: _PyImport_FindExtension() used to return a
borrowed reference, the "strong" reference being stored in the
PyImport_GetModuleDict() dictionary. All paths should behave the same.

See attached patch.

(for unit tests, run for example
    regrtest.py -R:: test_site
)

The patch looks good.  Benjamin will commit this.

Fixed in r66204.