Checkpoint.  A b it closer to working pickles and pickletools.
Added 'Y' getargs opcode which requires a bytes object.
diff --git a/Python/getargs.c b/Python/getargs.c
index 8331a18..0f6f21b 100644
--- a/Python/getargs.c
+++ b/Python/getargs.c
@@ -1099,6 +1099,15 @@
 			return converterr("string", arg, msgbuf, bufsize);
 		break;
 	}
+
+	case 'Y': { /* bytes object */
+		PyObject **p = va_arg(*p_va, PyObject **);
+		if (PyBytes_Check(arg))
+			*p = arg;
+		else
+			return converterr("bytes", arg, msgbuf, bufsize);
+		break;
+	}
 	
 	case 'U': { /* Unicode object */
 		PyObject **p = va_arg(*p_va, PyObject **);
@@ -1640,6 +1649,7 @@
 	/* object codes */
 
 	case 'S': /* string object */
+	case 'Y': /* string object */
 	case 'U': /* unicode string object */
 		{
 			(void) va_arg(*p_va, PyObject **);