Overcommit doesn't work with Stylelint 16 #823

Stylelint 16 made a breaking change: lint failures are now printed on stderr instead of stdout.

Overcommit hasn't yet been updated to support Stylelint 16, and still expects the output on stdout. As a result, the pre-commit hook prints "OK" when there are actual lint failures.

Stylelint documentation regarding the breaking change: https://stylelint.io/migration-guide/to-16#breaking-changes

I suspect the best way to solve this is for Overcommit to check both stderr and stdout, so that new and old versions of Stylelint are supported.