Auto merge of #3320 - str4d:macos-tests, r=bitcartel

Fix MacOS tests

Includes code cherry-picked from upstream PR bitcoin/bitcoin#8270.

src/test/bitcoin-util-test.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 # Copyright 2014 BitPay, Inc.
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.

src/test/buildenv.py.in

@@ -1,2 +1,2 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 exeext="@EXEEXT@"