The `:all` option runs both of these to produce a set of digested and non-digested assets.  As I understand it, the non-digested assets are useful for error pages. What I was seeing was when running `:primary` in the production environment, everything ran smoothly but when it tried to do `:nondigest` in production it was attempting to load more of the Rails environment and bailing on Gems it could not find.  This may be a quirk of non-digest mode, but I didn't dig to figure out why in an effort to get a fix out there.