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imp.load_module appears to have a regression - the file argument is not allowed to be None when loading a C_EXTENSION. The pywin32 post-install script for version 217 calls imp.load_module for a C extension with file=None, so presumably this worked in earlier versions.
Note that apparently pywin32 tip no longer calls load_module in this way, and load_module is marked as deprecated in the documentation, so it is not clear if this issue actually needs fixing.
See #15828 for some background.

How can you load a C extension without a file path? Are C extensions being inappropriately flagged as built-in modules on Windows? What does imp.find_module() return for the module being checked? I need more debugging info on what imp.find_module() and imp.load_module() returns in 3.2 and 3.3 before I can make a call on where the actual breakage is.

It's the open file object argument, not the path. I assume that if you
supplied None, the code opened the file for you.

Well, that's extremely annoying as that doesn't work for .py or .pyc files::
>>> import imp
>>> stuff = imp.find_module('blah')
>>> stuff
(<_io.TextIOWrapper name=4 mode='U' encoding='utf-8'>, 'blah.py', ('.py', 'U', 1))
>>> stuff[0].close()
>>> imp.load_module('blah', None, 'blah.py', stuff[2])
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
ValueError: file object required for import (type code 1)
I really hate these functions.

New changeset c0a21617dbee by Brett Cannon in branch '3.3':
Issue #15902: Fix imp.load_module() to accept None as a file when
http://hg.python.org/cpython/rev/c0a21617dbee
New changeset 322c556260d5 by Brett Cannon in branch 'default':
#15902: merge w/ 3.3
http://hg.python.org/cpython/rev/322c556260d5 

Leaving it up to the release manager to decide if this is worth cherrypicking or just waiting for the next bugfix release.

http://hg.python.org/cpython/rev/996a937cdf81 also applies to this.