Code review comment for ~raharper/curtin:fix/uefi-remove-dups-v2

CI failed because the latest versions of pyrsistent are not compatible with py27. Full CI run log at [1]. Can be worked around by pinning the version of pyrsistent:

https://code.launchpad.net/~paride/curtin/+git/curtin/+merge/390446

On the MP itself: do you think it's worth adding a "missing BootCurrent" test case?

[1] https://paste.ubuntu.com/p/fgGwqC6ktv/