[Bug 1417880] Re: Invisible prompts in do-release-upgrade

[Marius Gedminas]

The updated package finally reached Rackspace's Ubuntu mirror and I
tried to verify it on my 14.04 cloud VM.  Unfortunately the bug is still
present in ubuntu-release-upgrader 1:0.220.7 from trusty-proposed.

I can see that the new sys.stdout.flush() line is present in
/usr/lib/python3/dist-packages/DistUpgrade/DistUpgradeViewText.py of the
updated package, so I'm baffled as to what's going on.  Will try to
investigate.

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https://bugs.launchpad.net/bugs/1417880

Title:
  Invisible prompts in do-release-upgrade

Status in ubuntu-release-upgrader package in Ubuntu:
  Fix Released
Status in ubuntu-release-upgrader source package in Trusty:
  Fix Committed
Status in ubuntu-release-upgrader source package in Utopic:
  Fix Released

Bug description:
  [Impact]

  Users upgrading from 14.04 and 14.10 via the command line "do-release-
  upgrade" will not be able to do so unless they figure out that they
  need to press "y" and Enter (without the benefit of a prompt).

  [Test Case]

  On an affected system, run 'sudo do-release-upgrade'

  When it asks if you want to continue doing this over SSH, the text
  ends with a blank line.  If you press Enter at this point, only then
  will you get to see the prompt, which was

      Continue?  [yN]

  but by then it's too late and you already chose "no" by pressing
  Enter.

  [Regression Potential]

  The patch itself is quite small, just flushing output whenever we
  prompt the user.  Should be safe.

  [Original Report]

  I'm upgrading an Ubuntu 14.04 LTS system to 14.10 over ssh with 'sudo
  do-release-upgrade'.

  When it asks me if I want to continue doing this over SSH, the text
  ends with a blank line.  If I press Enter at this point, only then I
  get to see the prompt, which was

      Continue?  [yN]

  but by then it's too late and I already chose "no".

  The same thing happens if I restart, go past this prompt (without
  seeing it), then ask for details about package
  removals/upgrades/installs.  I get a list of packages in a pager.
  When I quit (by pressing q) I should once more see the prompt asking
  me if it's okay and if I should proceed, or cancel, or see the details
  again.  But the prompt isn't there and doesn't appear until after I
  input my answer.

  I think there's a missing sys.stdout.flush() call somewhere in do-
  release-upgrade.

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: ubuntu-release-upgrader-core 1:0.220.6
  ProcVersionSignature: Ubuntu 3.13.0-39.66-generic 3.13.11.8
  Uname: Linux 3.13.0-39-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3.6
  Architecture: amd64
  CrashDB: ubuntu
  Date: Wed Feb  4 08:16:03 2015
  InstallationDate: Installed on 2012-11-02 (823 days ago)
  InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
  PackageArchitecture: all
  SourcePackage: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to trusty on 2015-02-04 (0 days ago)

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