Suppress error msg in admin panel

I am doing some web page development work at a location with no internet connection. My Lenovo Thinkpad ia my workstation, then I use a 1 m crossed cable and a Intel NUC / Centos 7 server with newest WordPress 4.8 and a modified 2012 theme using a Child Theme. I am developing a “learning system” with some houndreds of web pages. Content is critical. Design is not so critical.

One small problem is that I gat a error msg each time I post or update a page, saying the site can not load Google fonts. (As ther is no Internet connection.) How do I disable the loading of Google fonts or eventually, how can I disable this error msg?

Failed to load content css: https://fonts.googleapis.com/css?family=Open+Sans:400italic%2C700italic%2C400%2C700&subset=latin%2Clatin-ext