GKE api fails with cidr conflict

gke.py

import string
import random
from google.cloud import container_v1
from google.api_core.retry import Retry
from pprint import pprint


cluster = {
  "name": "cluster-" + ''.join(random.choice(string.ascii_lowercase) for i in range(8)),
  "master_auth": {
  },
  "logging_service": "logging.googleapis.com/kubernetes",
  "monitoring_service": "monitoring.googleapis.com/kubernetes",
  "network": "default",
  "node_pools": [
    {
      "name": "default-pool",
      "config": {
        "machine_type": "n1-standard-1",
        "disk_size_gb": 100,
        "oauth_scopes": [
          "https://www.googleapis.com/auth/devstorage.read_only",
          "https://www.googleapis.com/auth/logging.write",
          "https://www.googleapis.com/auth/monitoring",
          "https://www.googleapis.com/auth/servicecontrol",
          "https://www.googleapis.com/auth/service.management.readonly",
          "https://www.googleapis.com/auth/trace.append"
        ],
        "metadata": {
          "disable-legacy-endpoints": "True",
          "blablabla": "momomo"
        },
        "image_type": "COS",
        "service_account": "default",
        "preemptible": True,
        "disk_type": "pd-standard",
        "shielded_instance_config": {
          "enable_integrity_monitoring": True
        }
      },
      "initial_node_count": 1,
      "autoscaling": {
        "enabled": True,
        "min_node_count": 1,
        "max_node_count": 3
      },
      "management": {
        "auto_upgrade": True,
        "auto_repair": True
      },
    }],
  "ip_allocation_policy": {
    "use_ip_aliases": True,
    "create_subnetwork": True,
    "cluster_ipv4_cidr_block": "/19"
  }
}

cm = container_v1.ClusterManagerClient()
operation = cm.create_cluster(
    parent='projects/PRODUCT_ID/locations/europe-west2',
    cluster=cluster, retry=Retry()
)

pprint(operation)