No warning of missing templates

[UltraNurd]

I was getting some weird behavior (while parsing List of Governors of Alabama, for what it's worth) where table cells that should have contained ArticleLinks contained just newlines. I quickly realized that the cause must be that they were wrapped in the {{sortname}} template, but it wasn't until after a lot of digging inside core.py and expander.py that I determined that it was because that template didn't exist.

As it happens, I was working with a small subset of pages in my CDB, which among other things had filtered out templates. I realize this is a noob mistake to leave out the templates, but it would have been helpful if getParsedArticle had printed a warning or thrown an exception instead of just silently deleting apparently simple page content. I'm not sure what the best way to do this is, or if it's even widely desirable behavior, so I don't have a specific patch proposal.