gem install chef fails with this message
The reason being that chef 11.0.0 is dependent net-ssh ~> 2.2.2 and net-ssh-multi ~> 1.1.0. And net-ssh-multi 1.1.1 which was was released on Feb 6 2013 is dependent on net-ssh >= 2.6.4.
In the short-term it seems like net-ssh-multi should be locked at = 1.1. In the long term chef should probably be checked or update for compatibility with recent versions of net-ssh