This question has been asked before here (404 error when using brew to install mysql), but unfortunately the fix doesn't work for me. I have already ran brew update, so I'm up to date.
I'm on the latest version of MacOS 10.12 and I am running Xcode 8 if that matters.
brew install mysql
Warning: You are using OS X 10.12.
We do not provide support for this pre-release version.
You may encounter build failures or other breakages.
==> Downloading https://cdn.mysql.com/Downloads/MySQL-5.7/mysql-boost-5.7.11.tar.gz
curl: (22) The requested URL returned error: 404 Not Found Error:
Failed to download resource "mysql" Download failed:
The 5.7.11 mysql download you reference no longer exists (it certainly is 404).
Looking at the homebrew formula for mysql, it has been updated to point to the latest mysql version.
So it seems that you are not in fact up to date. Try running
brew update twice, then
brew doctor and fix any warnings.
There have been some big changes in homebrew over the last 9 months, if you have an old install it might be easier to uninstall totally. There are also several ownership and directory location changes that need to be straightened out with the upgrade to homebrew 1.0