One alternative would look like
import ctypes
sizeof_int = ctypes.sizeof(ctypes.c_int)
FICLONE = (1073741824 % 256**sizeof_int) | 37897 | (sizeof_int << 16)
but, even if the above really(?) is a 100% correct Python port of
$ echo FICLONE | cpp -include linux/fs.h | tail -n 1
it still seems more likely that the ctypes package is somehow buggy
somewhere than for Qubes storage to run on an exotic architecture with
non 32 bit ints (in the foreseeable future).
So just document the baked in assumption.
d7478d128b