lazymanifest: fail if path or hash strings cannot be created

While generating (path, hash, flags), we fail if flags cannot be
created. We should also fail if path or hash cannot be created.

mercurial/manifest.c

@@ -243,7 +243,7 static PyObject *lmiter_iternext(PyObjec
 	consumed = pl + 41;
 	flags = PyString_FromStringAndSize(l->start + consumed,
 									   l->len - consumed - 1);
-	if (!flags) {
+	if (!path || !hash || !flags) {
 		goto bail;
 	}
 	ret = PyTuple_Pack(3, path, hash, flags);