BUG/MINOR: spoa-server: fix size_t format printing

From https://www.python.org/dev/peps/pep-0353/
"A new type Py_ssize_t is introduced, which has the same size as the
compiler's size_t type, but is signed. It will be a typedef for ssize_t
where available."

For integer types, causes printf to expect a size_t-sized integer
argument.

This should fix github issue #702

This should be backported to >= v2.2

Signed-off-by: William Dauchy <[email protected]>

Author: wdauchy

ps_python.c

@@ -66,7 +66,7 @@ static int ps_python_check_overflow(Py_ssize_t len)
 	 */
 	if (len >= (Py_ssize_t)INT_MAX) {
 		PyErr_Format(spoa_error,
-				"%d is over 2GB. Please split in smaller pieces.", \
+				"%zd is over 2GB. Please split in smaller pieces.", \
 				len);
 		return -1;
 	} else {