Merge "Fix doc generation for python 3"

api-ref/source/conf.py

@@ -158,8 +158,8 @@ pygments_style = 'sphinx'
 # html_last_updated_fmt = '%b %d, %Y'
 git_cmd = ["git", "log", "--pretty=format:'%ad, commit %h'", "--date=local",
            "-n1"]
-html_last_updated_fmt = subprocess.Popen(
-    git_cmd, stdout=subprocess.PIPE).communicate()[0]
+html_last_updated_fmt = subprocess.check_output(
+    git_cmd).decode('utf-8')
 
 # If true, SmartyPants will be used to convert quotes and dashes to
 # typographically correct entities.