docs: def check_environment(provider_conf):
      """Check all ressources needed by Enos."""
      session = get_session()
      image_id = check_glance(session, provider_conf.image)
      flavor_to_id, id_to_flavor = check_flavors(session)
      ext_net, network, subnet = check_network(
          session,
          provider_conf.configure_network,
          provider_conf.network,
          subnet=provider_conf.subnet,
          dns_nameservers=provider_conf.dns_nameservers,
          allocation_pool=provider_conf.allocation_pool)
  
      return {
          'session': session,
          'image_id': image_id,
          'flavor_to_id': flavor_to_id,
          'id_to_flavor': id_to_flavor,
          'ext_net': ext_net,
          'network': network,
          'subnet': subnet
      }