When the 'powersave' option under 'system console' was defined but no actual serial console device this cause the following error during migration:
Loading configuration from 'config.boot'
Traceback (most recent call last):
File "/opt/vyatta/etc/config-migrate/migrate/system/16-to-17", line 45, in <module>
for device in config.list_nodes(base + ['device']):
File "/usr/lib/python3/dist-packages/vyos/configtree.py", line 236, in list_nodes
raise ConfigTreeError("Path [{}] doesn't exist".format(path_str))
vyos.configtree.ConfigTreeError: Path [b'system console device'] doesn't exist