Solution adapted from:

https://groups.google.com/forum/#!topic/py-leveldb/VpVtc9hJatw

diff -Nurp leveldb-0.194.orig/leveldb_ext.h leveldb-0.194/leveldb_ext.h

--- leveldb-0.194.orig/leveldb_ext.h	2016-09-16 19:05:03.000000000 -0500

+++ leveldb-0.194/leveldb_ext.h	2018-10-24 17:38:06.381639156 -0500

@@ -4,9 +4,11 @@

 #ifndef __LEVELDB__MODULE__H__

 #define __LEVELDB__MODULE__H__

-extern "C" {

+extern "C++" {

 #include <Python.h>

+}

+extern "C" {

 #include "structmember.h"

 #include <stdlib.h>