I don't know why but `Rails.logger` is still nil when evaluated from
`configure` block in `config/environments/development.rb`. The only way
I found to make ActiveSupport's cache to use the default logger is from
an initializer.
Note that `ActiveSupport::Cache::Store` uses `debug` level and so we
need to set the dev logger in that same level to see its messages. If
you want to debug in staging as well, you'll need to modify the log
level manually.
fede58289b