Raise custom auth error, re-raise on failed re-auth

app/services/lndhub.rb

@@ -26,7 +26,7 @@ class Lndhub
     data = JSON.parse(res.body)
 
     if data.is_a?(Hash) && data["error"] && data["message"] == "bad auth"
-      raise "BAD_AUTH"
+      raise AuthError
     else
       data
     end