[Bug 1511875] [NEW] Can't upgrade from 15.10 Wily to 16.04 Xenial in LXC container

[MegaBrutal]

Public bug reported:

When I try to upgrade from 15.10 Wily to 16.04 Xenial (actual
development version) within an LXC container, the upgrade script hangs
at the message „Calculating the changes”.

Steps to reproduce:
1. Make an LXC container with Wily (quickest option is to use lxc-create -t download, choose ubuntu, wily, amd64/i386).
2. Boot up the container, log in, „apt-get -y install ubuntu-release-upgrader”.
3. Start the upgrade with „do-release-upgrade -d”.

You will see that the upgrade process will hang at the message
„Calculating the changes”.

The process which hangs: „/usr/bin/python3 /tmp/ubuntu-release-upgrader-
1mpotr5d/xenial --mode=server --frontend=DistUpgradeViewText --devel-
release”

With strace, it is revealed that the process hangs at a „futex” system call:
futex(0x7f4190000c10, FUTEX_WAIT_PRIVATE, 0, NULL

This system call never returns, the process must be interrupted with
CTRL-C or kill.

Upgrading to any previous release within an LXC container works without
problems, therefore I consider it as a regression.

** Affects: lxc (Ubuntu)
     Importance: Undecided
         Status: New

** Affects: ubuntu-release-upgrader (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: regression-release wily xenial

** Also affects: lxc (Ubuntu)
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1511875

Title:
  Can't upgrade from 15.10 Wily to 16.04 Xenial in LXC container

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