replace error-chain with a maintained framework

[ninewise]

At the time of writing, thiserror or anyhow seem fine. The former seems more similar to error-chain, but the latter seems easier to use overall.

Perhaps also check other dependencies.

[rien]

It seems that thiserror is better for libraries (when the resulting errrors should be easy to handle by implementors), while anyhow is better for applications (when you just want simple and clean user-facing error handling).