old_contents: class McDatabaseHandlerException(Exception):
      """Database handler exception."""
      pass
  
  
  class McConnectException(McDatabaseHandlerException):
      """__connect() exception."""
      pass
  
  
  class McSchemaIsUpToDateException(McDatabaseHandlerException):
      """schema_is_up_to_date() exception."""
      pass
  
  
  class McQueryException(McDatabaseHandlerException):
      """query() exception."""
      pass
  
  
  class McPrimaryKeyColumnException(McDatabaseHandlerException):
      """primary_key_column() exception."""
      pass
  
  
  class McFindByIDException(McDatabaseHandlerException):
      """find_by_id() exception."""
      pass
  
  
  class McRequireByIDException(McDatabaseHandlerException):
      """require_by_id() exception."""
      pass
  
  
  class McUpdateByIDException(McDatabaseHandlerException):
      """update_by_id() exception."""
      pass
  
  
  class McDeleteByIDException(McDatabaseHandlerException):
      """delete_by_id() exception."""
      pass
  
  
  class McCreateException(McDatabaseHandlerException):
      """create() exception."""
      pass
  
  
  class McUniqueConstraintException(McDatabaseHandlerException):
      """create() exception."""
      pass
  
  
  class McFindOrCreateException(McDatabaseHandlerException):
      """find_or_create() exception."""
      pass
  
  
  class McQuoteException(McDatabaseHandlerException):
      """quote() exception."""
      pass
  
  
  class McPrepareException(McDatabaseHandlerException):
      """prepare() exception."""
      pass
  
  
  class McTransactionException(McDatabaseHandlerException):
      """Exception thrown on transaction problems."""
      pass
  
  
  class McBeginException(McTransactionException):
      """begin() exception."""
      pass
  
new_contents: class McDatabaseHandlerException(Exception):
      """Database handler exception."""
      pass
  
  
  class McConnectException(McDatabaseHandlerException):
      """__connect() exception."""
      pass
  
  
  class McQueryException(McDatabaseHandlerException):
      """query() exception."""
      pass
  
  
  class McPrimaryKeyColumnException(McDatabaseHandlerException):
      """primary_key_column() exception."""
      pass
  
  
  class McFindByIDException(McDatabaseHandlerException):
      """find_by_id() exception."""
      pass
  
  
  class McRequireByIDException(McDatabaseHandlerException):
      """require_by_id() exception."""
      pass
  
  
  class McUpdateByIDException(McDatabaseHandlerException):
      """update_by_id() exception."""
      pass
  
  
  class McDeleteByIDException(McDatabaseHandlerException):
      """delete_by_id() exception."""
      pass
  
  
  class McCreateException(McDatabaseHandlerException):
      """create() exception."""
      pass
  
  
  class McUniqueConstraintException(McDatabaseHandlerException):
      """create() exception."""
      pass
  
  
  class McFindOrCreateException(McDatabaseHandlerException):
      """find_or_create() exception."""
      pass
  
  
  class McQuoteException(McDatabaseHandlerException):
      """quote() exception."""
      pass
  
  
  class McPrepareException(McDatabaseHandlerException):
      """prepare() exception."""
      pass
  
  
  class McTransactionException(McDatabaseHandlerException):
      """Exception thrown on transaction problems."""
      pass
  
  
  class McBeginException(McTransactionException):
      """begin() exception."""
      pass
  
subject: Remove unused exception