There isn't really much "-m test" can do to flag this - multiprocessing is making assumptions about the meaning of __file__ that may be flat out invalid when -m is used to execute the main module.

Fixing that properly is going to require a PEP so the interpreter preserves the information that multiprocessing needs in order to spawn the child process correctly on Windows. (I already have that on my personal todo list for 3.3)

I'm not sure what to do for 3.2. We could comment out the assert, since that will be slightly less broken than the current total failure (it will still be slightly broken, though).