On ubuntu 18.04 it's not creating stylesheet.css

[Domingo Alvarez Duarte]

When following the documentation and try to Building the Documentation I'm getting this error and the file stylesheet.css is not created (maybe libsass version/bug ?):

./WebCooker
Error: Invalid CSS after "    background:": expected expression (e.g. 1px, bold), was "#80868b42;"
        on line 255 of ../../../../../repos/plywood/src/web/theme/layout.scss
>>     background: #80868b42;
   ----------------^

[Jeff Preshing]

Just reproduced. I guess older libsass don't recognize this color format. Fix on the way.