qubes-sync-time.service fails to start on Arch Linux because of Python2/3 issue

[fishilico]

Qubes OS version:

R4.0, with Arch Linux template built by following instructions from https://www.qubes-os.org/doc/building-archlinux-template/

Affected component(s):

qubes-sync-time.service (qvm-sync-clock systemd service)

---

Steps to reproduce the behavior:

• Create a Arch Linux TemplateVM and an AppVM on Qubes OS R4.0.

• Enumerate the services which failed to start (systemctl | grep failed). There is:

  * qubes-sync-time.service   loaded failed failed    Update time from ClockVM
  

• Try to start the service, it fails again.

• Start the program used by the service from a shell:

$ sudo /usr/bin/qvm-sync-clock
Traceback (most recent call last):
  File "/usr/lib/qubes/qubes-sync-clock", line 38, in <module>
    main()
  File "/usr/lib/qubes/qubes-sync-clock", line 35, in main
    stdout=subprocess.DEVNULL)
AttributeError: 'module' object has no attribute 'DEVNULL'

subprocess.DEVNULL only exists in Python 3, but /usr/lib/qubes/qubes-sync-clock starts with:

#!/usr/bin/python2

The source code used python3 (https://github.com/QubesOS/qubes-core-agent-linux/blob/v4.0.26/qubes-rpc/qubes-sync-clock#L1) but the Arch Linux package replaces every Python shebang with Python 2 (https://github.com/QubesOS/qubes-core-agent-linux/blob/v4.0.26/archlinux/PKGBUILD#L48-L52):

    # Force running all scripts with python2
    sed 's:^#!/usr/bin/python.*:#!/usr/bin/python2:' -i misc/*
    sed 's:^#!/usr/bin/env python.*:#!/usr/bin/env python2:' -i misc/*
    sed 's:^#!/usr/bin/python.*:#!/usr/bin/python2:' -i qubes-rpc/*
    sed 's:^#!/usr/bin/env python.*:#!/usr/bin/env python2:' -i qubes-rpc/*

As /usr/lib/qubes/qubes-sync-clock is not compatible with Python 2, /usr/bin/qvm-sync-clock fails, and so does the service qubes-sync-time.service.

Expected behavior:

qubes-sync-time.service works fine.

Actual behavior:

qubes-sync-time.service fails to start, because it tries to run Python 3 code with Python 2.

General notes:

There seems to be an ongoing effort to make Arch Linux packages use Python 3 Qubes libraries (e.g. QubesOS/qubes-core-qubesdb@5efa37d ). This issue may be solved by ensuring every Python library used to interact with Qubes OS from an Arch Linux template is installed in its Python 3 version.

---

Related issues:

I opened this issue because I have not found any issue related to migrating to Python 3.
It might be related to the more general "Archlinux template for QubesOS 4.0" issue, #3185