The Pageviews API returns "no data found". In this case, we might query the Revision API to see if the page was recently created, and show a more user-friendly message that the pageview data is not yet available, and to check back the following day. If the Revision API says the page doesn't exist, we can explain that to the user. If the page does exist, is not new, and the Pageviews API returns not found, it probably means no pageviews have been recorded yet, and we can safely put in zeros into the timeseries for that article.