Raise exception if no session is created
Raise exception if no session is created

If the clientmanager is unable to create a keystone session (due to
insufficient auth parameters or something else) then the exception
caused by this shouldn't be ignored, as was the case.

On the other hand, we don't want this behaviour in the case of the
'complete' command, so this is now properly detected.

Change-Id: If4f453d23cc87900cda752e9ffbcf41ded59e26f
Closes-Bug: #1444640

openstack/python-openstackclient,BjoernT/python-openstackclient,redhat-openstack/python-openstackclient,dtroyer/python-openstackclient,redhat-openstack/python-openstackclient,dtroyer/python-openstackclient,BjoernT/python-openstackclient,openstack/python-openstackclient