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Date:   Thu, 5 Mar 2020 22:34:16 +0100
From:   Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
To:     Markus Heiser <markus.heiser@darmarit.de>
Cc:     "Bird, Tim" <Tim.Bird@sony.com>, Jonathan Corbet <corbet@lwn.net>,
        "tbird20d@gmail.com" <tbird20d@gmail.com>,
        "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] scripts/sphinx-pre-install: add '-p python3' to
 virtualenv
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Em Wed, 4 Mar 2020 10:20:34 +0100
Markus Heiser <markus.heiser@darmarit.de> escreveu:

> 
> Am 04.03.20 um 09:31 schrieb Mauro Carvalho Chehab:
> > Em Wed, 4 Mar 2020 07:20:48 +0100
> > Markus Heiser <markus.heiser@darmarit.de> escreveu:
> >> With py3 the recommended way to install virtual environments is::
> >>
> >>     python3 -m venv sphinx-env
> >>
> >> This (python3) is what worked for me on RHEL/CentOS (dnf),
> >> archlinux and debian/ubuntu (tested from 16.04 up to 20.04).
> > 
> > Hmm... from:
> > 
> > 	https://packaging.python.org/guides/installing-using-pip-and-virtual-environments/
> > 
> > This works since Python version 3.3. It sounds doable to use it.
> > 
> > Yet, if we'll be switching to this method, the script should check if
> > the version is 3.3 or newer. The logic inside get_sphinx_fname() would
> > also require some changes, as it won't need to install anymore the
> > virtualenv program for Python >= 3.3.
> 
> I guess you can ignore 3.2 and downwards
> 
>    https://en.wikipedia.org/wiki/History_of_Python#Table_of_versions
> 
> Support for py2.7 and >=py3.3 should match nearly all use cases / distributions 
> we support.
> 
> BTW: starting scripts with:
> 
> -m <module-name>
>      Searches sys.path for the named module and runs the
>      corresponding .py file as a script.
> 
> is mostly more robust.  The option exists also in py2.  From py3.3 on
> a subset of virtualenv is built-in, so you can run '-m venv' ot of the
> box.

I did some tests... as everything with python, it is not so simple...
The thing is that "-mvenv" requires a python module called "ensurepip".

On Fedora, openSuse and archlinux, this is installed together with
python3, but Debian maintainers had a different idea about how to package it.
There, ensurepip is inside a python3-venv-3.x (where x is 5, 6 or 7 -
depending on the Ubuntu/Debian version, and if backports repository is
been used or not).

There is a package python3-venv too, with installs the right package,
together with some unneeded stuff (pyvenv, with is a deprecated script). 

Yet, installing python3-venv seems to be a reliable way to install
the proper package without having to deal with more fragile heuristics.

I'm working on some patches that should hopefully add support for
using "python3 -mvenv", but testing it is not trivial, as I want
to ensure that it won't cause troubles on other distros. So, I'm
installing a myriad of distros with lxc, in order to test how the
script will actually work with some different environments.

Thanks,
Mauro