Submits RST_STREAM frame to cancel/reject the stream *stream_id*
with the error code *error_code*.

The pre-defined error code is one of :enum:`nghttp2_error_code`.

The *flags* is currently ignored and should be
:enum:`nghttp2_flag.NGHTTP2_FLAG_NONE`.

This function returns 0 if it succeeds, or one of the following
negative error codes:

:enum:`nghttp2_error.NGHTTP2_ERR_NOMEM`
    Out of memory.
:enum:`nghttp2_error.NGHTTP2_ERR_INVALID_ARGUMENT`
    The *stream_id* is 0.