def get_building_of_entry(service_dict):
    """Extract the configured building constraint from an yaml service entry

    :service_dict: service dict from yaml
    :returns: building that is set
    """
    # get constraints
    constraint_list = service_dict['deploy']['placement']['constraints']
    # convert them to dicts
    label_dict = {i.split("==")[0].strip(): i.split("==")[1].strip()
                  for i in constraint_list}
    return label_dict.get('node.labels.building')