Fix?

config/config.exs

@@ -22,3 +22,6 @@ use Mix.Config
 # here (which is why it is important to import them last).
 #
 #     import_config "#{Mix.env}.exs"
+
+config :logger, :console,
+  level: :debug

lib/kv/registry.ex

@@ -1,10 +1,12 @@
 defmodule KV.Registry do
+    require Logger
     ## Client API
 
     @doc """
     Starts the registry.
     """
     def start_link(event_manager, buckets_supervisor, opts \\ []) do
+        Logger.debug "#{__MODULE__}.start_link(#{inspect event_manager},#{inspect buckets_supervisor},#{inspect opts})"
         GenServer.start_link(__MODULE__, {event_manager, buckets_supervisor}, opts)
     end
 

lib/kv/supervisor.ex

@@ -57,7 +57,7 @@ defmodule KV.Supervisor do
             worker(GenEvent, [[name: @manager_name]]),
 #            supervisor(KV.BucketAndRegistrySupervisor, [[name: @bucket_and_reg_sup_name]])
             supervisor(KV.Bucket.Supervisor, [[name: @bucket_sup_name]]),
-            worker(KV.Registry, [@manager_name, [name: @registry_name]])
+            worker(KV.Registry, [@manager_name, :buckets_supervisor_missing_here, [name: @registry_name]])
         ]
         IO.puts "Supervising children: #{inspect children}"
         supervise(children, strategy: :one_for_one)