Investigate mass disappearance of media links

[hancush]

On 3/27, media links disappeared from all events on the Board Agendas site. Our scrape logs indicate that this disappearance and subsequent reappearance happened all at once, suggesting that something upstream went wrong. I've outlined what happened, as well as how we scrape media links, in this document: https://docs.google.com/document/d/1kqqs46T8wuSt3xpcK8REwBA_QxVPV-cwA4FQAmfuMec/edit?usp=sharing

@camachoo is going to sync with Granicus to see if our theory of a temporary blip in Legistar is feasible. This will help to determine next steps, if any.

[hancush]

I will mark Granicus maintenance on our calendar so we can be aware of potential issues: https://status.granicus.com/

[hancush]

This seems to happen very rarely. If we continue to see this type of issue, however, it could be useful for pupa to send an alert if all objects (or some high threshold of objects) are updated in a single scrape. I will open an issue over in that repo to bookmark that idea.

[hancush]

Opened opencivicdata/pupa#340, will drop into deep freeze unless something like this recurs.