import paramiko

ssh_client = paramiko.SSHClient()
ssh_client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh_client.connect('192.168.122.55', username='user', password='password')
transport = ssh_client.get_transport()
session = transport.open_session()

session.request_x11()
stdin = session.makefile('wb')
stdout = session.makefile('rb')
stderr = session.makefile_stderr('rb')
session.exec_command('env; xterm')
transport.accept()

print 'Exit status:', session.recv_exit_status()
print 'stdout:n{}'.format(stdout.read())
print 'stderr:n{}'.format(stderr.read())
session.close()

Exit status: 1
stdout:
SHELL=/bin/bash
XDG_SESSION_COOKIE=8025e1ba5e6c47be0d2f3ad6504a25ee-1347286654.617967-1932974971
SSH_CLIENT=192.168.122.1 58654 22
USER=user
MAIL=/var/mail/user
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games
PWD=/home/user
LANG=en_US.UTF-8
SHLVL=1
HOME=/home/user
LOGNAME=user
SSH_CONNECTION=192.168.122.1 58654 192.168.122.55 22
DISPLAY=localhost:10.0
_=/usr/bin/env

stderr:
xterm: Xt error: Can't open display: localhost:10.0

ssh -X user@192.168.122.55 'env; xterm'