fix setbranch command for python2

Author: LD250

jenkins_cli/cli.py

@@ -1,7 +1,8 @@
 from __future__ import print_function
 import os
-from time import time, sleep
+import sys
 import datetime
+from time import time, sleep
 import jenkins
 import socket
 from xml.etree import ElementTree
@@ -64,6 +65,10 @@ def get_jobs_legend():
     return legend
 
 
+def xml_to_string(root):
+    return ElementTree.tostring(root, encoding=('unicode' if sys.version_info[0] == 3 else None))
+
+
 class CliException(Exception):
     pass
 
@@ -192,7 +197,7 @@ def setbranch(self, args):
         scm_name, branch_node = self._get_scm_name_and_node(root)
         if branch_node is not None:
             branch_node.text = args.branch_name
-            new_xml = ElementTree.tostring(root, encoding='unicode')
+            new_xml = xml_to_string(root)
             self.jenkins.reconfig_job(job_name, new_xml)
             print('Done')
         else: