This had already been identified and "fixed" on Wednesday, probably
around the time the bug was filed (I uploaded the main-menu update
around 11h30 EST). For posterity, I've captured relevant information at
http://people.canonical.com/~mtrudel/lp1694531/)

Unfortunately, it's just the kind of bug that is genuinely hard to
recognize and debug unless you have a good understanding of how d-i
works; so I'll explain for the future:

We uploaded a libdebian-installer change on May 24th, which did some
changes to the symbols provided by that library. It looked tame to me,
so I sponsored the changes and did not insist on rebuilding the reverse-
dependencies immediately as non of them relied on the exact symbols
changed (SHA256 support). Namely, main-menu and netcfg were identified
as needing a rebuild eventually, and needing a merge. Someone else had
started doing d-i merges.

In preparing the netcfg merge and other changes, while testing I noticed
that d-i would not start correctly. You'd reach the "d-i screen", but
you would see the screen flicker, restarting repeatedly, forever. A
little bit of debugging (starting the installer in expert mode, command-
line, using the mini.iso image) and with the knowledge that the screen
flickers after loading what looks like the d-i background, it's likely
the main menu or some part of the early steps (language/keyboard
selection, etc) that fail, as well as the messages already shown here in
screenshots, I identified main-menu as the culprit. /sbin/debian-
installer is a short script that just runs other pieces, some of which
can be quickly dismissed as unlikely to apply to a default install,
which helps narrowing things down.

Running main-menu from the console (ctrl-alt-f2) yields an error (see
screenshot included in my capture of relevant files). This makes it
apparent that the issue is related to libdebian-installer, which was
changed with a date greater than main-menu's last upload. Rebuilding
main-menu would be a reasonable attempt to fix the bug, but given that
we were lagging a bit behind Debian, it was merged. main-menu was
directly uploaded to the archive since the merge changes were
straightforward and correct (and the merge obviously needed to be done
anyway).

The important part when changing d-i components, however, is that some
of them are so important that they are also used during d-i's build
process, so as to be included in main.iso. They are listed under build
/pkg-lists in the d-i source tree. main-menu is listed in build/pkg-
lists/base. When listed, the packages are included in mini.iso, and thus
require a debian-installer rebuild when changed. debian-installer was
also uploaded in a PPA for testing with main-menu.

After verifying that the mini.iso image booted fine, I contacted Adam
Conrad to synchronize on the necessary debian-installer upload, since he
routinely does d-i uploads for new kernels. d-i was uploaded to artful
and published in -proposed on 2017-05-29, and finally migrated to
-release at 2017-06-01 16:54:47 EDT; the following ubuntu-server
(20170602) includes all fixes.

Once thing to notice is that 20170602 is still listed under ubuntu-
server/daily/pending rather than ubuntu-server/daily/current (the image
in /current is the previous-last-known-good image 20170524). This means
there may be other issues that break successful completion of the whole
set of ubuntu-server tests.

http://people.canonical.com/~mtrudel/lp1694531 includes a copy of a
broken mini.iso image, along with a screenshot of the real error from
main-menu. The diff for the libd-i update is available here:
http://launchpadlibrarian.net/320240937/libdebian-
installer_0.102ubuntu3_0.110ubuntu1.diff.gz

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https://bugs.launchpad.net/bugs/1694531

Title:
  17.10 Install Fails to Start

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