How to make PostgreSQL default_tablespace work properly?
Per the PostgreSQL tablespaces documentation:


  If a database is created without specifying a tablespace for it, it
  uses the same tablespace as the template database it is copied from.


Per the CREATE DATABASE documentation:


  By default, the new database will be created by cloning the standard
  system database template1.


You could either alter the template1 database's tablespace to screwy, or create a new template database that has a tablespace of screwy, then specify that new database as a template when creating your screwy database.