Creates a #GTask and then immediately calls gio.task.Task.returnError
on it. Use this in the wrapper function of an asynchronous method
when you want to avoid even calling the virtual method. You can
then use gio.async_result.AsyncResult.isTagged in the finish method wrapper to
check if the result there is tagged as having been created by the
wrapper method, and deal with it appropriately if so.
Creates a #GTask and then immediately calls gio.task.Task.returnError on it. Use this in the wrapper function of an asynchronous method when you want to avoid even calling the virtual method. You can then use gio.async_result.AsyncResult.isTagged in the finish method wrapper to check if the result there is tagged as having been created by the wrapper method, and deal with it appropriately if so.
See also gio.task.Task.reportNewError.