Why can't I install Sass on Mac OS Sierra?

Question

I have tried installing Sass three times on Mac OS Sierra(10.12) from the terminal typing the following code:

sudo gem install sass

Then it

Answer 1

I used to have the same problem installing the Sass.
After installing Xcode with

xcode-select --install  

I agree the license with

sudo xcodebuild -license  

and finally run the app Xcode and finished installing.
After that I write sudo gem install sass and it works.