If a user is asked to log in, they're left hanging at Meta at the OAuth authorization dialog.

The flow is something like this:

1. Get rate limited and asked to log in	2. Click 'Allow' at Meta	3. The download starts, and you're still at Meta

After which, the only option on screen is to click 'Cancel' to abort the OAuth, which doesn't actually do anything at that point.

Looks likely to be a simple fix. The log in link is currently e.g.

https://ws-export.wmcloud.org/login?callback=https://ws-export.wmcloud.org/oauth_callback?redirect%3Dhttps://ws-export.wmcloud.org/?fonts%253D%2526format%253Depub-3%2526lang%253Den%2526page%253DEmma

but should instead have title rather than page:

https://ws-export.wmcloud.org/login?callback=https://ws-export.wmcloud.org/oauth_callback?redirect%3Dhttps://ws-export.wmcloud.org/?fonts%253D%2526format%253Depub-3%2526lang%253Den%2526title%253DEmma

The downside with that however is that they'll be redirected back to the export form and have to click export again. That feels better than the alternative though, and it also means that (after T311100) they'll see a log out link and so know that they are in fact logged in.