Custom "Authorization Required" Message on Login Page?

Is there a simple way to edit the message that displays on the login page when using this plugin?
Right now it says "Authorization Required: This blog may only be viewed by users who are subscribed to this blog" and I just want to change the text of that message.

I found this thread ( detailing a fix with a child theme, but I'm looking for something simpler.

P.S. I am also planning to use the plugins Login Message and Ultimate Branding to customize the login screen, if that makes a difference. Thanks!