gem install cannot download from rubygems.org

Question

When I type

gem install sass

I get the following error message

C:>gem install compass ERROR: Could not

Answer 1

TL;DR Apply the official fix:

1. Download https://rubygems.org/downloads/rubygems-update-2.6.7.gem

2. Run:

   gem install --local rubygems-update-2.6.7.gem
   update_rubygems --no-ri --no-rdoc
   gem uninstall rubygems-update -x
   

Long version

See http://guides.rubygems.org/ssl-certificate-update/ .

Basically it adds GlobalSignRootCA. Very easy to apply, unfortunately hard to google though.