Fix an apparent typo.  This test of the readonly boolean should have been != 0
rather than >= 0.  This change means the PyBUF_LOCK flag to the buffer api
works on immutable bytes objects as one would expect.
diff --git a/Objects/abstract.c b/Objects/abstract.c
index 655a52a..c0298a8 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -673,7 +673,7 @@
 {
 	if (view == NULL) return 0;
 	if (((flags & PyBUF_LOCK) == PyBUF_LOCK) &&
-	    readonly >= 0) {
+	    readonly != 0) {
 		PyErr_SetString(PyExc_BufferError,
 				"Cannot lock this object.");
 		return -1;