I don't think GetChannelCred() should be failing in normal circumstances. There is currently a bug where an app "pending" publishing does not receive back the credentials (that should be fixed soon). But that serves as great illustration to "expect the unexpected", i.e. that many calls relying on external resources may fail - and to think what to do about it in each case.
Before you were using GetPartialUserData() to base account on email addy, yes? So what was your fallback if that fails, the same should apply here. In fact, if it were me i think i would use the email-way as a fallback for GetChannelCred(). The mere reason of avoiding publishing/review delays might make me do that (how are they going to test, if it always dead-ends at "Unable To Fetch User Credentials"?)