Ubuntu-boot error message on UC20 UEFI

[snowsky]

@snowsky

There will be > 1 assertion files besides model assertion file. Should we merge them together as an input of ubuntu-image command? Before I used cloud-init file to create a user for uc18, I guess we cannot do the same for uc20.

A quick update, I created an assertion according to https://ubuntu.com/core/docs/system-user. The command “make-system-user” generated the assertion file named “auto-import.assert”.