class Net::SSH::Authentication::Agent

def negotiate!

if the version could not be negotiated successfully.
Attempts to negotiate the SSH agent protocol version. Raises an error 
def negotiate!
  # determine what type of agent we're communicating with
  type, body = send_and_wait(SSH2_AGENT_REQUEST_VERSION, :string, Transport::ServerVersion::PROTO_VERSION)
  raise AgentNotAvailable, "SSH2 agents are not yet supported" if type == SSH2_AGENT_VERSION_RESPONSE
  if type == SSH2_AGENT_FAILURE
    debug { "Unexpected response type==#{type}, this will be ignored" }
  elsif type != SSH_AGENT_RSA_IDENTITIES_ANSWER1 && type != SSH_AGENT_RSA_IDENTITIES_ANSWER2
    raise AgentNotAvailable, "unknown response from agent: #{type}, #{body.to_s.inspect}"
  end
end