I don't remember more than one test failing without ExtFile - I expect it's
the one for which you have the fix (although I think it failed in a slightly
different way if ExtFile was present).
However, the ExtFile tests gave me 26 Failures and 3 Errors with Silva but
without PIL, so it might be worth mentioning that if you want to install ExtFile
it's probably also a good idea to get PIL as well.