Agent admitted failure to sign using the key

If you get this whle connecting over SSH:

Agent admitted failure to sign using the key

You should add the keys by executing:

ssh-add

If you see something like this next ssh-agent is not running - then you should start it:

eval $(ssh-agent)

You can also add this to ~/.bashrc in order to not run it on every login:

eval $(ssh-agent)
ssh-add