I know this is an old post and Ryan hopefully found the answer he was looking for. But since the page still ranks and people stilll look for a solution (as I just did), I would like to point to the same question in another thread with a very straightforward answer by Anthony Madrigal:
https://groups.google.com/forum/#!topic/adwords-scripts/GUECDB5FjP8
He said, that you need to find this line: UrlFetchApp.fetch(url, {muteHttpExceptions: true}).getResponseCode();
And change it by this here: UrlFetchApp.fetch(url, {muteHttpExceptions: true,followRedirects:false}).getResponseCode();
Augusto