gulp-sass 5 does not have a default Sass compiler; please set one yourself.
Both the `sass` and `node-sass` packages are permitted.
For example, in your gulpfile:
var sass = require('gulp-sass')(require('sass'));
background: url("data:image/svg+xml, --- --- --- ") center no-repeat;
background: url("data:image/svg+xml, --- --- --- ") center no-repeat,
url("data:image/svg+xml, --- --- --- ") center no-repeat,
url("data:image/svg+xml, --- --- --- ") center no-repeat;