Issue #10783: Fix test_sys, pack('c', ' ') => pack('c', b' ')

Lib/test/test_sys.py

@@ -569,7 +569,7 @@ class SizeofTest(unittest.TestCase):
     TPFLAGS_HEAPTYPE = 1<<9
 
     def setUp(self):
-        self.c = len(struct.pack('c', ' '))
+        self.c = len(struct.pack('c', b' '))
         self.H = len(struct.pack('H', 0))
         self.i = len(struct.pack('i', 0))
         self.l = len(struct.pack('l', 0))