py23 Use bytechr() instead of chr()
diff --git a/Lib/fontTools/cffLib.py b/Lib/fontTools/cffLib.py
index 7a74041..bc4cbbd 100644
--- a/Lib/fontTools/cffLib.py
+++ b/Lib/fontTools/cffLib.py
@@ -614,13 +614,13 @@
 	return value
 
 def writeCard8(file, value):
-	file.write(chr(value))
+	file.write(bytechr(value))
 
 def writeCard16(file, value):
 	file.write(struct.pack(">H", value))
 
 def packCard8(value):
-	return chr(value)
+	return bytechr(value)
 
 def packCard16(value):
 	return struct.pack(">H", value)
@@ -635,9 +635,9 @@
 	d = {}
 	for op, name, arg, default, conv in table:
 		if isinstance(op, tuple):
-			op = chr(op[0]) + chr(op[1])
+			op = bytechr(op[0]) + bytechr(op[1])
 		else:
-			op = chr(op)
+			op = bytechr(op)
 		d[name] = (op, arg)
 	return d