Don't exit with error on HTTP 403 when downloading clone bundle

If the server returns HTTP 403 (forbidden) when attempting to
download clone bundle files, ignore it and continue, rather than
exiting with a fatal error.

Change-Id: Icf78cba0332b51b0e7b622f7c7924369b551b6f6

repo

@@ -428,7 +428,7 @@ def _DownloadBundle(url, local, quiet):
     try:
       r = urllib.request.urlopen(url)
     except urllib.error.HTTPError as e:
-      if e.code == 404:
+      if e.code in [403, 404]:
         return False
       print('fatal: Cannot get %s' % url, file=sys.stderr)
       print('fatal: HTTP error %s' % e.code, file=sys.stderr)