reqwest: "Too many open files" w/ Async Client

I’ve been developing the tooling for an apt replacement with the async client, which may need to fetch a couple dozen files at the same time (depending on how many sources are active and what files those sources’ release files point to).

The following error occurs when sharing a single async::Client across all connections:

Is this something that could be handled better by reqwest? Perhaps return a NotReady when there’s too many files open.