Issue #5640: Fix _multibytecodec so that CJK codecs don't repeat
error replacement returned by codec error callbacks twice in
IncrementalEncoder and StreamWriter.
diff --git a/Modules/cjkcodecs/multibytecodec.c b/Modules/cjkcodecs/multibytecodec.c
index 9846465..c6b3492 100644
--- a/Modules/cjkcodecs/multibytecodec.c
+++ b/Modules/cjkcodecs/multibytecodec.c
@@ -506,7 +506,6 @@
 		outleft = (Py_ssize_t)(buf.outbuf_end - buf.outbuf);
 		r = codec->encode(state, codec->config, &buf.inbuf, inleft,
 				  &buf.outbuf, outleft, flags);
-		*data = buf.inbuf;
 		if ((r == 0) || (r == MBERR_TOOFEW && !(flags & MBENC_FLUSH)))
 			break;
 		else if (multibytecodec_encerror(codec, state, &buf, errors,r))
@@ -536,6 +535,7 @@
 		if (_PyBytes_Resize(&buf.outobj, finalsize) == -1)
 			goto errorexit;
 
+	*data = buf.inbuf;
 	Py_XDECREF(buf.excobj);
 	return buf.outobj;