Script crashes with "TypeError: int() argument must be a string or a number, not 'NoneType'" message

tools/bisect-builds.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Snapshot Build Bisect Tool
 
 This script bisects a snapshot archive using binary search. It starts at
 a bad revision (it will try to guess HEAD) and asks for a last known-good
 revision. It will then binary search across this revision range by downloading,
@@ skipping 251 matching lines @@
       return None
     data = json.loads(response.read()[4:])
     if 'message' in data:
       message = data['message'].split('\n')
       message = [line for line in message if line.strip()]
       search_pattern = re.compile(SEARCH_PATTERN[depot])
       result = search_pattern.search(message[len(message)-1])
       if result:
         return result.group(1)
     print 'Failed to get svn revision number for %s' % git_sha1
-    return None
+    raise ValueError
 
   def _GetSVNRevisionFromGitHashFromGitCheckout(self, git_sha1, depot):
     def _RunGit(command, path):
       command = ['git'] + command
       if path:
         original_path = os.getcwd()
         os.chdir(path)
       shell = sys.platform.startswith('win')
       proc = subprocess.Popen(command, shell=shell, stdout=subprocess.PIPE,
                               stderr=subprocess.PIPE)
       (output, _) = proc.communicate()
 
       if path:
         os.chdir(original_path)
       return (output, proc.returncode)
 
     path = None
     if depot == 'blink':
       path = os.path.join(os.getcwd(), 'third_party', 'WebKit')
     if os.path.basename(os.getcwd()) == 'src':
       command = ['svn', 'find-rev', git_sha1]
       (git_output, return_code) = _RunGit(command, path)
       if not return_code:
         return git_output.strip('\n')
-      return None
+      raise ValueError
     else:
       print ('Script should be run from src folder. ' +
              'Eg: python tools/bisect-builds.py -g 280588 -b 280590' +
              '--archive linux64 --use-local-repo')
       sys.exit(1)
 
   def GetSVNRevisionFromGitHash(self, git_sha1, depot='chromium'):
     if not self.use_local_repo:
       return self._GetSVNRevisionFromGitHashWithoutGitCheckout(git_sha1, depot)
     else:
@@ skipping 694 matching lines @@
              "you might also want to do a Blink bisect.")
 
     print 'CHANGELOG URL:'
     if opts.official_builds:
       print OFFICIAL_CHANGELOG_URL % (min_chromium_rev, max_chromium_rev)
     else:
       print '  ' + CHANGELOG_URL % (min_chromium_rev, max_chromium_rev)
 
 if __name__ == '__main__':
   sys.exit(main())