PostgreSQL: set default privileges on schemas themselves?
As mentioned by @a_horse_with_no_name, this is now implemented in PostgreSQL v10


  ALTER DEFAULT PRIVILEGES allows you to set the privileges that will be applied to objects created in the future. (It does not affect privileges assigned to already-existing objects.) Currently, only the privileges for schemas, tables (including views and foreign tables), sequences, functions, and types (including domains) can be altered.


Example,

ALTER DEFAULT PRIVILEGES
  GRANT USAGE ON SCHEMAS
  TO role;