Add `as` namespace to validation error CSS class name

[coryschires]

Everywhere else we use namespace CSS selectors with as. It makes sense to use the namespace on error as well - especially since error is a commonly used class name and thus there's a high likelihood that it could cause namespace collisions.

[coryschires]

Hey. Sorry to be making changes again so quickly but I believe this corrects a small oversight on my part. I don't imagine it will be too controversial of a merge.

Thanks!

[knalli]

No problem, thank you!