Fix catalog error
Fix catalog error

Use get() function to get 'catalog'

Change-Id: I4f48643097dc841312d6f048a9cceeb6e6d1ea76

openstack/python-openstacksdk,dudymas/python-openstacksdk,openstack/python-openstacksdk,mtougeron/python-openstacksdk,stackforge/python-openstacksdk,dtroyer/python-openstacksdk,dtroyer/python-openstacksdk,briancurtin/python-openstacksdk,stackforge/python-openstacksdk,briancurtin/python-openstacksdk,mtougeron/python-openstacksdk,dudymas/python-openstacksdk