Issue 4192 - getBuildNum must return a string

packager.py

 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 # Note: These are the base functions common to all packagers, the actual
 # packagers are implemented in packagerGecko and packagerChrome.
 
 import sys
 import os
 import re
@@ skipping 27 matching lines @@
 
 
 def getBuildNum(baseDir):
     try:
         from buildtools.ensure_dependencies import Mercurial, Git
         if Mercurial().istype(baseDir):
             result = subprocess.check_output(['hg', 'id', '-R', baseDir, '-n'])
             return re.sub(r'\D', '', result)
         elif Git().istype(baseDir):
             result = subprocess.check_output(['git', 'rev-list', 'HEAD'], cwd=baseDir)
-            return len(result.splitlines())
+            return str(len(result.splitlines()))
     except subprocess.CalledProcessError:
         pass
 
     return '0'
 
 
 def getBuildVersion(baseDir, metadata, releaseBuild, buildNum=None):
     version = metadata.get('general', 'version')
     if not releaseBuild:
         if buildNum == None:
@@ skipping 80 matching lines @@
         names = self.keys()
         names.sort(key=sortKey)
         for name in names:
             zip.writestr(name, self[name])
         zip.close()
 
     def zipToString(self, sortKey=None):
         buffer = StringIO()
         self.zip(buffer, sortKey=sortKey)
         return buffer.getvalue()