Nginx Docker build failing on Ubuntu

My Docker build is failing:

sudo docker build -t nginx_img_1 .

W: Failed to fetch http://ift.tt/1n3qDAe  404  Not Found [IP: 91.189.91.15 80]

W: Failed to fetch http://ift.tt/1wIgwSS  404  Not Found [IP: 91.189.91.15 80]

Why is this not working?

I cannot find the correct location on the http://ift.tt/P3bamR website.

When I google for binary-amd64 site: archive.ubuntu.com, I get a broken link.

Background: I am using an AWS instance of Ubuntu. I'm trying to build a Docker image with nginx.

Before I tried to do the Docker build, some instructions directed me to enter this line into /etc/apt/sources.list:

deb http://ift.tt/u86xTH raring main universe

Other web pages led me to think that the error I am getting can be circumvented by using this line instead in /etc/apt/sources.list:

deb http://ift.tt/12S3fMk raring main universe

This URL and the words after it ("raring main universe") seem to be participating in a dynamically constructed path at the time of the Docker build. But the error message I got was the same. So the sources.list file must not be where the problem is.

I'm trying to follow these directions: http://ift.tt/1vKXDCU