Issue 2956 - Ensure the correct version of jsshell is present

utils.py

 # coding: utf-8
 
 # This Source Code is subject to the terms of the Mozilla Public License
 # version 2.0 (the "License"). You can obtain a copy of the License at
 # http://mozilla.org/MPL/2.0/.
 
 from contextlib import closing
 import os
 import platform
 from StringIO import StringIO
 import sys
 import urllib
 import zipfile
 
-JSSHELL_VERSION = "31.5.0"
+JSSHELL_DIR = "mozilla-esr31"
 JSSHELL_URL = ("https://ftp.mozilla.org/pub/mozilla.org/firefox/nightly"
-               "/2015/02/2015-02-25-00-22-19-mozilla-esr31/jsshell-%s.zip")
+               "/2015/02/2015-02-25-00-22-19-%s/jsshell-%%s.zip" % JSSHELL_DIR)
 
 JSSHELL_SUPPORTED_PLATFORMS = {
   "win32": "win32",
   "linux2": {
     "i686": "linux-i686",
     "x86_64": "linux-x86_64"
   },
   "darwin": "mac"
 }
 
 def ensureJSShell():
   baseDir = os.path.dirname(__file__)
-  shell_dir = os.path.join(baseDir, "jsshell-%s" % JSSHELL_VERSION)
+  shell_dir = os.path.join(baseDir, JSSHELL_DIR)
 
   if not os.path.exists(shell_dir):
     os.makedirs(shell_dir)
   if sys.platform == 'win32':
     path = os.path.join(shell_dir, 'js.exe')
   else:
     path = os.path.join(shell_dir, 'js')
 
   if os.path.exists(path):
     return path
@@ skipping 13 matching lines @@
 
   if not os.path.exists(path):
     raise Exception('Downloaded package didn\'t contain JS shell executable')
 
   try:
     os.chmod(path, 0700)
   except:
     pass
 
   return path