[Python-3000] py3k conversion docs?

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I'm looking at the recently submitted patch for the csv module and am
scratching my head a bit trying to understand the code transformations.
I've not looked at any py3k code yet, so this is all new to me.  Is there
any documentation about the Py3k conversion?  I'm particularly interested in
the string->unicode conversion.

Here's one confusing conversion.  I see PyString_FromStringAndSize replaced
by PyUnicode_FromUnicode.  In another place I see PyString_FromString
replaced by PyUnicodeDecodeASCII.  In some places I see a char left alone.
In other places I see it replaced by PyUNICODE.

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