Fixing Raspbian apt source list

(Originally published 3/28/17)

Updating via apt suddenly stopped working for me today on both my Raspberry Pis with one on Jessie and the other one on Wheezy (it got stuck on waiting for headers). Took me a while before I figured the mirror director was the problem (I guess there is a outage with one of the mirrors). Inside the apt source list, commenting out the mirror director entry and replacing it which fixed it.