Attempting to access restricted files results in a 500 response

[paul-butcher]

See Slack.

Attempting to fetch a restricted file via https://api.wellcomecollection.org/text/alto/ results in a 500 response.

I do not know whether:
a) This should be 401 (i.e. it is caused by an unauthorised user trying to fetch the file and it is currently rightly refusing, but giving the wrong response)
b) There is actually something wrong (i.e. an authorised user is trying to fetch the file)

[paul-butcher]

There may be something else at play here. It is unlikely that a user has constructed the URLs I'm seeing by themselves, so are we incorrectly presenting links to restricted content? Perhaps someone has an old version of a page before the restriction was added?