"Warning: Symbol is not Defined"

[mbuttler]

Hi Folks,

I'm having an issue with this plugin when I connect through CircleCI to run a deployment task. It seems to fail when it goes to read my existing CSS file before building a purified, minified CSS file with the error "Symbol is not defined".

I'm not sure what it's talking about, because this script worked previously without issue and nothing has been changed with regard to the CSS in my project. It also works fine on my local machine, but not through Circle.