GetErrorBody will return the user-visible error message given an error.

GetStatusCode will return the status code associated with an error, and default_code if none is found.

OverrideErrorBody returns an ErrorOption (for use in ErrorClass creation or error instantiation) that controls the error body seen by GetErrorBody.

RestoreDefaultErrorBody returns an ErrorOption (for use in ErrorClass creation or error instantiation) that restores the default error body shown by GetErrorBody for some subhierarchy of errors.

SetStatusCode returns an ErrorOption (for use in ErrorClass creation or error instantiation) that controls the error's HTTP status code.