Subject: bug#468: python platform.linux_distribution() returns debian

From: Peter Duffy <[email-masked]>
Date: Thu, 21 May 2020 16:33:35 +0100

Package: libpython2.7-minimal
Version: 2.7.13

Environment in which bug seen: Devuan 2.1 (ascii)

Problem behaviour: python function platform.linux_distribution() returns
"debian" instead of "devuan"

To reproduce: 

(from command-line):
python

(from python prompt):
import platform
platform.linux_distribution()

(should return: "('debian','9','')"

quit()

Test fix:

platform.linux_distribution() tries to use the file /etc/lsb-release.
This doesn't appear to exist either in Debian stretch or Devuan ascii -
unless it's present in a package which isn't included in the default
install. Creating it with appropriate values fixes the problem:

Check whether /etc/lsb-release exists: it shouldn't, - but if so,
rename it (and rename it back after the test).

lsb_release -a > /etc/lsb-release

Edit /etc/lsb-release and change as follows:

"Distributor ID: " => "DISTRIB_ID="
"Description: " => "DISTRIB_DESCRIPTION="
"Release: "     => "DISTRIB_RELEASE="
"Codename: "    => "DISTRIB_CODENAME="

Above test should now return: "('Devuan','2.1','ascii')"

Additional information:

The problem is apparently caused by the combination of the absence
of /etc/lsb-release, and the presence of /etc/debian_release. The
algorithm in platform.linux_distribution() is apparently to try
reading /etc/lsb-release, and if it doesn't exist, look for any file
matching /etc/*_(version|release)

The bug also exists in python3 (package libpython3.5-minimal, version
3.5.3) - to reproduce, repeat the above test using "python3" instead of
"python"

The bug also exists in beowulf

Not sure whether above "fix" is feasible in practice - maybe other
python-based packages rely on getting back "debian" from
platform.linux_distribution()?

This problem came to light because it breaks the waagent package -
because it believes that it's running on debian, waagent tries to use
systemd-based commands and functions. I'm currently working this
problem, but I'm approaching it by putting in place internal tests to
ascertain whether debian or devuan, rather than relying on a
system-level fix. 

platform.linux_distribution() is deprecated and slated for removal

If it's decided that this can be safely fixed by
creating /etc/lsb-release, one question needs answering: whether to
lowercase the DISTRIB_ID field, or to leave it as returned by
lsb_release