Lookup a Scottish postcode. 

Returns Scottish Postcode Directory (SPD) data associated with postcode. At the moment this is just Scottish Parliamentary Constituency.

Returns `404` if postcode does not exist in SPD or is not valid.

For postcodes not in SPD but in ONSPD, 404 is returned with error message Postcode exists in ONSPD but not in SPD.

Source: Scottish Postcode Directory
