check also for closure test data in read_replica_pseudodata

Created by: RoyStegeman

This adds functionality to the read_replica_pseudodata function to ensure it also checks for the existence of closure test pseuodata.

Also, in the previous implementation the except statements were chained in a way that made the code act different from expected. Namely, both except statements correspond to the error raised under try (and not the second except corresponding to a potential error in the first except), as such the custom error was never raised.

(yes I think the nesting is a bit ugly, but I'm not aware of a better way with try-except)