Remove deprecated Error::description and Error::cause

[AnderEnder]

Error::description has been documented as soft-deprecated since 1.27.0 (17 months ago). It is going to be hard-deprecated soon(nightly/1.42). Error::cause has been documented as deprecated since 1.27.0, while Error::source was introduced.

This PR:

• Removes all implementations of description in error type
• Replaces cause with source

Related PR: rust-lang/rust#66919

[nox]

That's a breaking change and I'm not doing that any time soon.

[AnderEnder]

@nox , so what your suggestion? Deprecation is already merged and will be released in 1.42.

[nox]

I have no suggestion, I'm just saying that I'm not going to merge this any time soon. It's not like the deprecation is going to prevent building this crate anyway.

[kentfredric]

I suspect you could add a source implementation and leave the cause implementations intact, that way people using the old interfaces don't get broken, and eases the pain for those migrating to the new one... I suspect.

[nox]

@kentfredric The breaking change here is increasing the Rust minimum version.

[nox]

Wtf, never mind, I completely forgot source was added ages ago, my bad.

@AnderEnder I'll merge your PR if you revert the removal of description and cause, and just add source.

[AnderEnder]

@nox, I have created a new PR with your suggestion.