Creates a gstreamer.Task and then immediately calls 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 g_async_result_is_tagged() 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 gstreamer.Task and then immediately calls 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 g_async_result_is_tagged() 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 Task.reportNewError.