Permissions 0777 for '/Users/username/.ssh/id_rsa' are too open.
It is recommended that your private key files are NOT accessible by others.
This private key will be ignored.
解决方法，使用命令：

chmod 400 ~/.ssh/id_rsa
或者

chmod 600 ~/.ssh/id_rsa

参考：
https://stackoverflow.com/questions/9270734/ssh-permissions-are-too-open-error