reverted in master.. switching to jack_dev branch
wrapped a failing call to concat on empty string in lib/spree_active_shipping/engine.rb, line 35. my system had no app.config.spree.calculators.shipping_methods.
set default value of app.config.spree.calculators.shipping_methods to empty array. In my application's application.rb I now use a config.after_initialize block to add those spree_sctive_shipping calculators otherwise they do not show up in the admin under the shipping calc selector for a given shipping method.