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Subject: Re: [PATCH] scripts/sphinx-pre-install: add '-p python3' to
 virtualenv
To:     Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
        "Bird, Tim" <Tim.Bird@sony.com>
Cc:     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>
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From:   Markus Heiser <markus.heiser@darmarit.de>
Message-ID: <31a69fe7-c08d-9381-a111-5f522a4c9ffd@darmarit.de>
Date:   Wed, 4 Mar 2020 07:20:48 +0100
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Am 04.03.20 um 06:42 schrieb Mauro Carvalho Chehab:
> Em Tue, 3 Mar 2020 17:07:48 +0000
> "Bird, Tim" <Tim.Bird@sony.com> escreveu:
> 
>>> -----Original Message-----
>>> From: Jonathan Corbet <corbet@lwn.net>
>>>
>>> On Mon, 24 Feb 2020 18:34:41 -0700
>>> tbird20d@gmail.com wrote:
>>>    
>>>> With Ubuntu 16.04 (and presumably Debian distros of the same age),
>>>> the instructions for setting up a python virtual environment should
>>>> do so with the python 3 interpreter.  On these older distros, the
>>>> default python (and virtualenv command) might be python2 based.
>>>>
>>>> Some of the packages that sphinx relies on are now only available
>>>> for python3.  If you don't specify the python3 interpreter for
>>>> the virtualenv, you get errors when doing the pip installs for
>>>> various packages
>>>>
>>>> Fix this by adding '-p python3' to the virtualenv recommendation
>>>> line.
>>>>
>>>> Signed-off-by: Tim Bird <tim.bird@sony.com>
>>>
>>> I've applied this, even though it feels a bit fragile to me.  But Python
>>> stuff can be a bit that way, sometimes, I guess.
>>
>> I agree it seems a bit wonky.
> 
> Well, we could, instead, add some code that would be checking python and pip
> versions, but still distros could be doing some backports with could
> cause side-effects. So, checking for distro versions as done in this patch
> seems a lot safer.
> 
>> The less fragile approach would have been to just
>> always add the '-p python3' option to the virtualenv setup hint,
>> but Mauro seemed to want something more fine-tuned.
> 
> Yeah, I asked for a more fine-tuned version.
> 
> Depending on python/pip version, adding a -p python3 seems to cause
> troubles (at least I found some bug reports about that). I may be
> wrong (it was a long time ago), but, before adding the logic that checks
> for "python3" I guess I tried first add -p python3, but, back then,
> I found some troubles (probably with some old Fedora version).
> 
> So, better to use this syntax only on distros we know it will
> work as expected.
> 
>> As far as the string parsing goes, I think that the format of strings
>> returned by lsb-release (and the predecesors that sphinx_pre_install
>> checks) is unlikely to change.
> 
> Since when we added this script, we didn't have any troubles yet with
> the part of the code with checks the distribution version. So, I guess
> that the lsb-release related checks are pretty much reliable.
> 

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).

I am not familiar with the sphinx-pre-install script but may be
one of you is able to apply such a patch?


  -- Markus --