--- contrib/tools/python3/Modules/_blake2/blake2module.h	(index)
+++ contrib/tools/python3/Modules/_blake2/blake2module.h	(working tree)
@@ -2,7 +2,7 @@
 #define Py_BLAKE2MODULE_H
 
 #ifdef HAVE_LIBB2
-#include <blake2.h>
+#error #include <blake2.h>
 
 #else
 // use vendored copy of blake2