e322745763
boolean return value is not sufficient for representing the reason of error in most cases. For instance, any errors around new_sequence() would mean negotiation error, not just *ERROR*. And some subclasses will allocate buffer/memory/surface on new_picture() but it could be failed because of expected error, likely flushing Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1019>