It seems as though some people like me are experiencing a weird thing when upgrading mac these days, the RSA keys still work for connecting to things like GitHub but my keychain doesn't want to remember the password and is annoyingly asking me for it with every git push
.
The solution I found that works is at http://stackoverflow.com/a/41576222
Basically, edit my ~/.ssh/config
file to be:
Host *
UseKeychain yes