Not all exceptions are covered in pragmas (postgres)

[dctucker]

Building with 2.8.7 fails with the following error:

 Nim Output src/db.nim(47, 3) template/generic instantiation of `withDb` from here
        ... src/db.nim(48, 7) template/generic instantiation of `select` from here
        ... .nimble/pkgs2/norm-2.8.7-cdf05aec89e0c4f7ed7adb3ee60a3a7dff1c802c/norm/postgres.nim(261, 109) template/generic instantiation from here
        ... .nimble/pkgs2/norm-2.8.7-cdf05aec89e0c4f7ed7adb3ee60a3a7dff1c802c/norm/postgres.nim(290, 12) Error: fromRow(objs[i], row) can raise an unlisted exception: IOError

Either IOError (and possibly others) need to be added to the raises list of these functions, or the pragma should be removed entirely.