[Distutils] pip/easy_install mercurial in virtualenv on Python 3.3

Carl Meyer carl at oddbird.net
Mon Feb 25 18:38:37 CET 2013

On 02/25/2013 10:31 AM, Christian Tismer wrote:
> Actually, I would love to have both python2 and python3 in the same
> virtualenv, for testing purposes, distinguishing the versions by using
> the different interpreter, only.
> But installing both versions after another messes things up very much
> and led to the effect that I  always got python3, even if I explicitly ran
> (virtenv) $ python2
> Python 3.3.0 (default, Dec 29 2012, 18:23:00)
> ...

That's interesting. I'd expect that if you first created a venv using
Python 3, then removed the "python" symlink leaving only "python3", then
installed a Python 2 virtualenv in the same location, things would work
as you wish them to (at least on Linux/OSX; superimposed venvs don't
work at all on Windows AFAIK because the Lib directories aren't versioned).

>>> And who is responsible to make things "right":
>>> Should virtualenv avoid this naming problem,
>>> or should the mercurial installer become more carefully specify its
>>> interpreter?
>> In general, I think that it is wrong for system-installed scripts to
>> ever use "/usr/bin/env python" in the shebang line, as that makes it too
>> easy for them to be run with the wrong Python. I know that, for
>> instance, it is the policy of Debian/Ubuntu to not use "#!/usr/bin/env
>> python". I don't know what homebrew's policy is, but I'd suggest raising
>> this as a bug in the Homebrew Mercurial package.
> Thank you. Yes I feared that I would have to prove it to be a hg bug
> (again), not always the nicest experience ;-)

Well, let's distinguish between "Mercurial bug" and "bug in Homebrew
recipe for Mercurial" - usually the latter is the responsibility of
Homebrew, not Mercurial. I don't know what the Homebrew people will say,
but my guess is you are more likely to see this fixed at the Homebrew
level than in Mercurial itself.


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