WebSQL is guaranteed to throw an exception if the db isn't ready (i.e. the initial transaction has not completed yet).  You'll get something like 'SQLError: table meta-store does not exist`.

As for the stack trace, can't we just use `utils.inherits` and fix that for `PouchErrors`? If not, then just a generic Error object would be fine too, as long as we're consistent about the `name`.