Bug#802953: ess: install/ess may interact with console, fail emacs24 upgrade

[Hilko Bengen]

Package: ess
Version: 15.09-1
Severity: grave
Tags: patch

While upgrading emacs24 from 24.5+1-2 to 24.5+1-3 today, the
installation paused and I got the the following prompt:

,----
| Install ess for emacs24
| install/notmuch: Handling install for emacsen flavor emacs24
| install/notmuch: byte-compiling for emacs24
| gzip: Install.log.gz already exists; do you wish to overwrite (y or n)? 
`----

Pressing n caused the installation to fail:

,----
| gzip: Install.log.gz already exists; do you wish to overwrite (y or n)? n
|         not overwritten
| ERROR: install script from ess package failed
| dpkg: error while cleaning up:
|  subprocess installed post-installation script returned error exit status 1
`----

/usr/lib/emacsen-common/packages/install/ess wants to gzip its
install log which leads to the above prompt if the gzipped version
already exists, a violation of Debian Policy 3.9.1. "Prompting in
maintainer scripts".

Adding a simple "-f" when invoking gzip fixes this.

Cheers,
-Hilko

-- System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.2.0-1-amd64 (SMP w/6 CPU cores)
Locale: LANG=en_US.utf8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages ess depends on:
ii  dpkg            1.18.3
ii  emacsen-common  2.0.8
ii  install-info    6.0.0.dfsg.1-3

Versions of packages ess recommends:
ii  r-base-core  3.2.2-1

Versions of packages ess suggests:
pn  jags       <none>
pn  julia      <none>
pn  pspp       <none>
pn  xlispstat  <none>

-- no debconf information