I’m attempting to install a Hugo theme on my Micro.blog hosted blog. I’m getting this error. I vaguely understand it, but have no idea how to fix it. Suggestions?

Husband, dad, and nerd living in Auburn, AL and working in EdTech.
I’m attempting to install a Hugo theme on my Micro.blog hosted blog. I’m getting this error. I vaguely understand it, but have no idea how to fix it. Suggestions?