buildman: Convert to Python 3

Convert buildman to Python 3 and make it use that, to meet the 2020
deadline.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/buildman/buildman.py b/tools/buildman/buildman.py
index f17aa15..30a8690 100755
--- a/tools/buildman/buildman.py
+++ b/tools/buildman/buildman.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # SPDX-License-Identifier: GPL-2.0+
 #
 # Copyright (c) 2012 The Chromium OS Authors.
@@ -6,6 +6,8 @@
 
 """See README for more information"""
 
+from __future__ import print_function
+
 import multiprocessing
 import os
 import re
@@ -46,11 +48,11 @@
         suite = unittest.TestLoader().loadTestsFromTestCase(module)
         suite.run(result)
 
-    print result
+    print(result)
     for test, err in result.errors:
-        print err
+        print(err)
     for test, err in result.failures:
-        print err
+        print(err)
 
 
 options, args = cmdline.ParseArgs()