Revisions with hidden text break topic data generation

[ragesoss]

If a topic has an ArticleTimepoint where the revision breaks the WikiWho API, the topic can't be processed.

The immediate cause of the error is that the WikiWho API returns a 500 error for such a revision, raising an unhandled WikiWhoApi::RevisionTokenError from WikiWhoApi. Here's an example:

• Here's a revision: https://en.wikipedia.org/w/index.php?diff=1284698874
• Query that returns a 500 error: http://wikiwho-api.wmcloud.org/en/api/v1.0.0-beta/rev_content/rev_id/1284698874/?o_rev_id=true&editor=true&token_id=true&out=true&in=true

I'm not actually sure why this revision breaks WikiWho. Several revisions that follow were deleted, but not this one.

In any case, the system should be resilient to cases where one revision consistently errors, when WikiWho API is otherwise working normally.