class Net::SSH::Authentication::KeyManager

def initialize(logger, options={})

is not false.
use the ssh-agent if it is running and the `:use_agent` option
Create a new KeyManager. By default, the manager will 
def initialize(logger, options={})
  self.logger = logger
  @key_files = []
  @key_data = []
  @use_agent = !(options[:use_agent] == false)
  @known_identities = {}
  @agent = nil
  @options = options
end