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Date:   Sat, 22 Feb 2020 08:16:44 +0100
From:   Mauro Carvalho Chehab <mchehab@kernel.org>
To:     "Bird, Tim" <Tim.Bird@sony.com>
Cc:     "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        "corbet@lwn.net" <corbet@lwn.net>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: RFC: Fix for sphinx setup message
Message-ID: <20200222081644.4ce926a0@kernel.org>
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Hi Tim,

Em Fri, 21 Feb 2020 22:15:36 +0000
"Bird, Tim" <Tim.Bird@sony.com> escreveu:

> (Resend: Sorry for the dup.  I forgot to include the maintainers, and I had the LKML
> address wrong.) 
> 
> I was trying to set up my machine to do some documentation work, 
> and I had some problems with the sphinx install.  I figured out how to work
> around the issue, but I have a question about how to add the information
> to scripts/sphinx-pre-install (or whether it should go somewhere else).
> 
> Detailed messages below, but the TLl;DR is that I got the message:
> -------
> You should run:
> 
>     sudo apt-get install dvipng fonts-noto-cjk latexmk librsvg2-bin texlive-xetex
>     /usr/bin/virtualenv sphinx_1.7.9
>     . sphinx_1.7.9/bin/activate
>     pip install -r ./Documentation/sphinx/requirements.txt
>     ...
> ------
> 
> The pip install step didn't work, and I found that I needed to have everything
> based on python3 instead.  When I replaced:
>     /usr/bin/virtualenv sphinx_1.7.9
> with
>     /usr/bin/virtualenv -p python3 sphinx_1.7.9
> everything worked.
> 
> This message is coming from scripts/sphinx-pre-install (I believe on line 708).
> 
> Should I go ahead and submit a patch to add '-p python3' to that line?
> 
> Are there any downsides to enforcing that the virtualenv used for the
> documentation build use python3 only?

Actually, the script tries to detect if python3 is installed. Currently, it
does it by seeking for a python3 variant of virtualenv. If it finds, it
changes the recommendation accordingly. The actual code with does that is
this one:

	my $virtualenv = findprog("virtualenv-3");
	$virtualenv = findprog("virtualenv-3.5") if (!$virtualenv);
	$virtualenv = findprog("virtualenv") if (!$virtualenv);
	$virtualenv = "virtualenv" if (!$virtualenv);

This works fine on older Fedora distros (and probably CentOS/RHEL), where
there is a python3 variant of virtualenv. On Ubuntu (and Fedora 31), it
will just use virtualenv.

So, perhaps if we add something like this (untested):

	my $python = findprog("python3");

	if ($python)
		$virtualenv = "$virtualenv -p $python";

it would make the trick. Please notice, however, that this could cause
troubles with some distros that might have a version of virtualenv that
won't work with the above. So, perhaps we should add something like the
above inside give_debian_hints(), and either ensure that other Debian and 
Ubuntu LTS versions will work with such change, or add some checks for the
Ubuntu/Debian versions where we know this works.

Note: the version of the distribution (and its name) is already stored
at the global var $system_release.

Cheers,
Mauro