NVMe test failures in integration tests

In https://jenkins.ubuntu.com/server/job/curtin-vmtest-proposed-e/2/ we're seeing failures in the NVMe tests (for bionic and later) that look like this:

[ 316.702663] cloud-init[895]: Traceback (most recent call last):
[ 316.706636] cloud-init[895]: File "/curtin/curtin/commands/main.py", line 202, in main
[ 316.707961] cloud-init[895]: ret = args.func(args)
[ 316.708918] cloud-init[895]: File "/curtin/curtin/commands/block_discover.py", line 11, in block_discover_main
[ 316.710387] cloud-init[895]: print(json.dumps(block.discover(), indent=2, sort_keys=True))
[ 316.716316] cloud-init[895]: File "/curtin/curtin/block/__init__.py", line 1121, in discover
[ 316.720192] cloud-init[895]: return storage_config.extract_storage_config(probe_data.get('storage'))
[ 316.724117] cloud-init[895]: File "/curtin/curtin/storage_config.py", line 1128, in extract_storage_config
[ 316.726642] cloud-init[895]: found_cfgs, found_errs = parser.parse()
[ 316.729288] cloud-init[895]: File "/curtin/curtin/storage_config.py", line 577, in parse
[ 316.735945] cloud-init[895]: entry = self.asdict(data)
[ 316.739419] cloud-init[895]: File "/curtin/curtin/storage_config.py", line 692, in asdict
[ 316.742409] cloud-init[895]: "Couldn't find partition entry in table")