Consider constraining error types to a core::fmt::Debug

[shyndman]

I'm currently prototyping, and I'm rarely interested in the specifics of an error presented by the library.

Would there be any interesting in constraining the traits' associated Error types to core::fmt::Debug so they can be printed and forgotten, or passed along to anyhow! or whatever?

This would be a breaking change, obviously, but I'm curious whether you think this would be valuable? Or is flexibility in the interface more important to you?

[hannobraun]

I think that's reasonable. I can't think of a scenario where having your error types be Debug would not be acceptable.