I want to put the check as close to the connection attempt as possible, so that we catch when the call happens from a Builder and not just from the URI code. The `HIVE_METASTORE_URI_PROP` property seems appropriate for `HCatalog`, but the class isn't public and I'd rather not make it public just for the loader to reference one property. I thought duplication was an okay solution, but I can just have this reference the property in the Loader. Not a big deal.