Comment 1 for bug 2058870

Upgraded to Juju 3.4.0, trying to bootstrap, that's failing now, I believe it's due to the default VPC still in "custom" mode:

| [hloeung@dharkan juju]$ juju bootstrap google/asia-southeast1 haw-test-cloud-mirrors --bootstrap-series=focal --bootstrap-constraints mem=8G
| Creating Juju controller "haw-test-cloud-mirrors" on google/asia-southeast1
| Looking for packaged Juju agent version 3.4.0 for amd64
| Located Juju agent version 3.4.0-ubuntu-amd64 at https://streams.canonical.com/juju/tools/agent/3.4.0/juju-3.4.0-linux-amd64.tgz
| Launching controller instance(s) on google/asia-southeast1...
| ERROR failed to bootstrap model: cannot start bootstrap instance in any availability zone (asia-southeast1-b, asia-southeast1-a, asia-southeast1-c):
| starting bootstrap instance in zone "asia-southeast1-b": sending new instance request: sending new instance request: googleapi: Error 400: Invalid value for field 'resource.networkInterfaces[0]': '{ "network": "global/networks/default", "accessConfigs": [{ "type": "ONE_TO_ONE_NAT", "name"...'. Subnetwork should be specified for custom subnetmode network, invalid
| starting bootstrap instance in zone "asia-southeast1-a": sending new instance request: sending new instance request: googleapi: Error 400: Invalid value for field 'resource.networkInterfaces[0]': '{ "network": "global/networks/default", "accessConfigs": [{ "type": "ONE_TO_ONE_NAT", "name"...'. Subnetwork should be specified for custom subnetmode network, invalid
| starting bootstrap instance in zone "asia-southeast1-c": sending new instance request: sending new instance request: googleapi: Error 400: Invalid value for field 'resource.networkInterfaces[0]': '{ "network": "global/networks/default", "accessConfigs": [{ "type": "ONE_TO_ONE_NAT", "name"...'. Subnetwork should be specified for custom subnetmode network, invalid