old_contents: from .simple_broker import _DataBrokerClass, EventQueue, Header
  from .handler_registration import register_builtin_handlers
  
  DataBroker = _DataBrokerClass()  # singleton
  register_builtin_handlers()
  
new_contents: from .simple_broker import (_DataBrokerClass, EventQueue, Header,
                              LocationError, IntegrityError)
  from .handler_registration import register_builtin_handlers
  
  DataBroker = _DataBrokerClass()  # singleton
  register_builtin_handlers()
  
subject: Add Errors to the public API.