prow/slack/client.go
func (sl *Client) WriteMessage(text, channel string) error {
	sl.log("WriteMessage", text, channel)
	if sl.fake {
		return nil
	}

	var uv = sl.urlValues()
	uv.Add("channel", channel)
	uv.Add("text", text)

	_, err := sl.postMessage(chatPostMessage, uv)
	return err
}
func (sl *Client) WriteMessage(text, channel string) error {
	sl.log("WriteMessage", text, channel)
	if sl.fake {
		return nil
	}

	var uv = sl.urlValues()
	uv.Add("channel", channel)
	uv.Add("text", text)

	_, err := sl.postMessage(chatPostMessage, uv)
	return err
}
// WriteMessage adds text to channel