Dig into the failure more

This pull req doesn't fix anything, but shows how I dug deeper into your problem: I extract the SecTrustRef from the error and try to evaluate it myself. From a command-line build this fails with `kSecTrustResultOtherError`:

> A failure other than that of trust evaluation; for example, an internal failure of the SecTrustEvaluate function.

I think this means it's time to file a bug report.