Mysql2::Error: Can't connect to local MySQL server through socket '/tmp/mysql.sock'

I solved it!

First, go to database.yml

Change host: localhost to host: 127.0.0.1

That's it!

Edit: This works temporarily, but when I restarted my computer today it began throwing up the same errors. The fix was to just install mysql from the website, then my application could successfully connect to mysql again.