Deprecation warning for nested I18n namespace lookup no longer supported.

Hi, I'm not sure "I18n namespace lookup" mean but there's some
libraries (like https://github.com/nofxx/symbolize) that use nested
key in a way that I find perfectly logical, so I wonder if that
warning isn't superfluous as there might be a lot of useful ways to
leverage the AR locales that are legit and outside Rails control. In
the end I'm really not sure deprecation warnings make sense for what
is essentially data!

I was thinking about this and should this warning appear only for keys
which correspond to an actual attribute?