When reading config files, require them to be encoded with UTF-8.

[jaraco]

Closes #1702

Pull Request Checklist

• Changes have tests
• News fragment added in changelog.d. See documentation for details

[benoit-pierre]

Shouldn't the setuptools.unicode_utils.detect_encoding helper be removed?

[jaraco]

@pganssle I'd like to merge and release this today, so if you have any reservations, please let me know.

[pganssle]

I don't have a major problem with the idea. My over-cautious instinct is to deprecate first, but this is such an easy thing to fix if it breaks something that maybe it's not worth it?

(Famous last words)

[jaraco]

Good point. Here's my thinking: because the behavior was only recently released (January), probably not many project depend on the behavior or those that do are likely already cutting-edge enough to rely on this latest release. Moreover, if we find that releasing this does cause problems, I'll be on standby to release a bugfix release to add backward compatibility if needed (so only a small window of the problemmatic release).

[pganssle]

Oh if you are reversing a recently introduced behavior then I think it's even less likely to cause problems, I say go for it.

[jaraco]

Thanks both. In the interest of progress, I'm going to move forward with this, but don't hesitate to raise other concerns or thoughts.