When `-link` is used to link to an external API, the doclet tries to first find the `element-list` file for the API, and failing that, the `package-list` file.

However, if the server responds with a redirection to an error or other kind of page, instead of returning 404, that page will be read as if it is an element-list file.

This is bad.

The doclet does detect and handle redirections: but it should verify the result of any redirection is itself an `element-file` file, at least by its name.