2015-07-08 17:09:18 DEBUG 15301 (upgrade) BootstrapUpgrader: rollbacking...
2015-07-08 17:09:18 INFO 15301 (bootstrap) bootstrap upgrader: rollbacking...
2015-07-08 17:09:18 DEBUG 15301 (utils) Removing "/var/www/nailgun/6.0_bootstrap"
2015-07-08 17:09:18 DEBUG 15301 (utils) Copying "/var/www/nailgun/5.1.1_bootstrap" -> "/var/www/nailgun/bootstrap" [overwrite=1 symlinks=1]
2015-07-08 17:09:18 DEBUG 15301 (utils) Removing "/var/www/nailgun/bootstrap"
2015-07-08 17:09:19 INFO 15301 (bootstrap) bootstrap upgrader: rollbacked
2015-07-08 17:09:19 DEBUG 15301 (upgrade) HostSystemUpgrader: rollbacking...
2015-07-08 17:09:19 DEBUG 15301 (utils) Remove file "/etc/yum.repos.d/6.0_nailgun.repo"
2015-07-08 17:09:19 ERROR 15301 (upgrade) *** UPGRADE FAILED
2015-07-08 17:09:19 ERROR 15301 (cli) Shell command executed with "1" exit code: docker load < "/root/upgrade-6/upgrade/images/cobbler.tar"
Traceback (most recent call last):
  File "/root/upgrade-6/upgrade/.fuel-upgrade-venv/lib/python2.6/site-packages/fuel_upgrade/cli.py", line 177, in main
    run_upgrade(parse_args(sys.argv[1:]))
  File "/root/upgrade-6/upgrade/.fuel-upgrade-venv/lib/python2.6/site-packages/fuel_upgrade/cli.py", line 169, in run_upgrade
    upgrade_manager.run()
  File "/root/upgrade-6/upgrade/.fuel-upgrade-venv/lib/python2.6/site-packages/fuel_upgrade/upgrade.py", line 51, in run
    upgrader.upgrade()
  File "/root/upgrade-6/upgrade/.fuel-upgrade-venv/lib/python2.6/site-packages/fuel_upgrade/engines/docker_engine.py", line 85, in upgrade
    self.upload_images()
  File "/root/upgrade-6/upgrade/.fuel-upgrade-venv/lib/python2.6/site-packages/fuel_upgrade/engines/docker_engine.py", line 298, in upload_images
    utils.exec_cmd(u'docker load < "{0}"'.format(docker_image))
  File "/root/upgrade-6/upgrade/.fuel-upgrade-venv/lib/python2.6/site-packages/fuel_upgrade/utils.py", line 57, in exec_cmd
    _wait_and_check_exit_code(cmd, child)
  File "/root/upgrade-6/upgrade/.fuel-upgrade-venv/lib/python2.6/site-packages/fuel_upgrade/utils.py", line 108, in _wait_and_check_exit_code
    'exit code: {1} '.format(exit_code, cmd))
ExecutedErrorNonZeroExitCode: Shell command executed with "1" exit code: docker load < "/root/upgrade-6/upgrade/images/cobbler.tar"
==================================================
Upgrade failed