replace {:stop, reason} by :ignore to make sure start app never fail

lib/file_system/backend.ex

@@ -61,7 +61,7 @@ defmodule FileSystem.Backend do
     if os_type in module.supported_systems() do
       :ok
     else
-      Logger.error "The backend #{backend} you are using does NOT support your current system #{inspect os_type}."
+      Logger.error "The backend `#{backend}` you are using does NOT support your current system #{inspect os_type}."
       {:error, :unsupported_system}
     end
   end

lib/file_system/worker.ex

@@ -18,8 +18,8 @@ defmodule FileSystem.Worker do
       {:ok, backend} ->
         {:ok, backend_pid} = backend.start_link([{:worker_pid, self()} | Keyword.drop(args, [:backend])])
         {:ok, %{backend_pid: backend_pid, subscribers: %{}}}
-      {:error, reason} ->
-        {:stop, reason}
+      {:error, _reason} ->
+        :ignore
     end
   end