Fix for CONPY-279:

Allow None values for password and database in change_user()
method of connection object.

Author: 9EOR9

mariadb/mariadb_connection.c

@@ -624,7 +624,7 @@ PyObject *MrdbConnection_change_user(MrdbConnection *self,
     int rc= 0;
     MARIADB_CHECK_CONNECTION(self, NULL);
 
-    if (!PyArg_ParseTuple(args, "sss", &user, &password, &database))
+    if (!PyArg_ParseTuple(args, "szz", &user, &password, &database))
         return NULL;
 
     MARIADB_BEGIN_ALLOW_THREADS(self);

testing/test/integration/test_nondbapi.py

@@ -132,6 +132,16 @@ def test_escape(self):
         cursor.execute(cmd)
         del cursor
 
+    def test_conpy279(self):
+        conn = self.connection
+        default_conf = conf()
+        try:
+            conn.change_user(None, None, None)
+        except TypeError:
+            pass
+        conn.change_user(default_conf["user"], None, None)
+        conn.close()
+
 
 if __name__ == '__main__':
     unittest.main()