The patch looks alright. I don't like the documentation for
PyUnicode_FromFormatV, however. Here's my attempt to document it:

.. cfunction:: PyObject* PyUnicode_FromFormatV(const char *format,
va_list vargs)

   Equivalent to the function :cfunc:`PyUnicode_FromFormat`, except that
it takes a va_list instead of variable number of arguments.