port list_deliverable_branches.py to python 3

Depends-On: Ifb435ea9c5d99639e1562761f9c48cbefb9db57f
Change-Id: I89942097cb29aeeaafc19f6bf7e849ea6002a7fa
Signed-off-by: Doug Hellmann <doug@doughellmann.com>

jenkins/scripts/release-tools/list_deliverable_branches.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 #    Licensed under the Apache License, Version 2.0 (the "License"); you may
 #    not use this file except in compliance with the License. You may obtain
@@ -15,8 +15,6 @@
 """Lists the branches in the modified deliverable files.
 """
 
-from __future__ import print_function
-
 import argparse
 import os.path
 import re
@@ -35,7 +33,7 @@ def find_modified_deliverable_files(reporoot):
     results = subprocess.check_output(
         ['git', 'diff', '--name-only', '--pretty=format:', 'HEAD^'],
         cwd=reporoot,
-    )
+    ).decode('utf-8')
     filenames = [
         l.strip()
         for l in results.splitlines()
@@ -65,7 +63,7 @@ def get_modified_deliverable_file_content(reporoot, filenames):
         if not os.path.exists(filename):
             # The file must have been deleted, skip it.
             continue
-        with open(filename, 'r') as f:
+        with open(filename, 'r', encoding='utf-8') as f:
             deliverable_data = yaml.load(f.read())
 
         # Map the release version to the release contents so we can

jenkins/scripts/release-tools/py3-requirements.txt

@@ -0,0 +1,5 @@
+pbr>=1.4
+requests>=1.1
+PyYAML>=3.1.0
+zuul
+simplejson>=2.2.0