Modified fetch_audio_file to only pass success response body back

Author: deanshi

lib/pa_ess/updater.ex

@@ -166,8 +166,8 @@ defmodule PaEss.Updater do
     http_client = Application.get_env(:realtime_signs, :http_client)
 
     case http_client.get(url) do
-      {:ok, response} -> response.body
-      {:error, error} -> Logger.info("Error getting PCM file: #{error}")
+      {:ok, %HTTPoison.Response{status_code: status, body: body}} when status == 200 ->
+        body
     end
   end