PyArg_Parse with "u" format is deprecated.
ref: https://docs.python.org/3/c-api/arg.html#strings-and-buffers
See here. https://foss.heptapod.net/pypy/cffi/blob/branch/default/c/_cffi_backend.c#L4454-4455
Please use "U" and PyUnicode_AsWideCharString instead.