Bug#813226: tzdata config script ignores /etc/timezone on non-interactive configuration

[YAMADA Tsuyoshi <tyamada@minimum2scp.org>]

Package: tzdata
Version: 2016a-1
Severity: minor

Dear Maintainer,

After tzdata 2016a-1, automated tzdata configuration with

  echo "Asia/Tokyo" > /etc/timezone
  dpkg-reconfigure -fnoninteractive tzdata

does not work.

With tzdata 2015g-1, it works.

  root@a26eeeb7b8b7:~# date
  Sat Jan 30 15:28:54 UTC 2016
  root@a26eeeb7b8b7:~# echo Asia/Tokyo > /etc/timezone
  root@a26eeeb7b8b7:~# dpkg-reconfigure -fnoninteractive tzdata

  Current default time zone: 'Asia/Tokyo'
  Local time is now:      Sun Jan 31 00:29:12 JST 2016.
  Universal Time is now:  Sat Jan 30 15:29:12 UTC 2016.

  root@a26eeeb7b8b7:~# date
  Sun Jan 31 00:29:13 JST 2016

But with tzdata 2016a-1, it does not work well.

  root@fdc1139936e4:~# date
  Sat Jan 30 15:30:00 UTC 2016
  root@fdc1139936e4:~# echo Asia/Tokyo > /etc/timezone
  root@fdc1139936e4:~# dpkg-reconfigure -fnoninteractive tzdata

  Current default time zone: 'Etc/UTC'
  Local time is now:      Sat Jan 30 15:30:21 UTC 2016.
  Universal Time is now:  Sat Jan 30 15:30:21 UTC 2016.

  root@fdc1139936e4:~# date
  Sat Jan 30 15:30:23 UTC 2016

I have found a workaround, deleting /etc/localtime
before running dpkg-reconfigure solves this problem.

  root@fdc1139936e4:~# date
  Sat Jan 30 15:30:50 UTC 2016
  root@fdc1139936e4:~# echo Asia/Tokyo > /etc/timezone
  root@fdc1139936e4:~# rm /etc/localtime
  root@fdc1139936e4:~# dpkg-reconfigure -fnoninteractive tzdata

  Current default time zone: 'Asia/Tokyo'
  Local time is now:      Sun Jan 31 00:31:15 JST 2016.
  Universal Time is now:  Sat Jan 30 15:31:15 UTC 2016.

  root@fdc1139936e4:~# date
  Sun Jan 31 00:31:18 JST 2016

Is this bug of tzdata config script? Or expected behavior?

-- System Information:
Debian Release: stretch/sid
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'unstable'), (500, 'testing'),
(500, 'stable'), (1, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 4.3.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=ja_JP.utf8, LC_CTYPE=ja_JP.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages tzdata depends on:
ii  debconf [debconf-2.0]  1.5.58

tzdata recommends no packages.

tzdata suggests no packages.

-- debconf information:
  tzdata/Zones/SystemV:
  tzdata/Zones/Antarctica:
  tzdata/Zones/Pacific:
  tzdata/Zones/Atlantic:
* tzdata/Zones/Asia: Tokyo
* tzdata/Zones/Etc: UTC
  tzdata/Zones/US:
  tzdata/Zones/Europe:
  tzdata/Zones/Australia:
  tzdata/Zones/Africa:
* tzdata/Areas: Asia
  tzdata/Zones/Arctic: