[TIP] Tox and setup.py enforcing python version

[Roy Wright]

Thank you. 

The [tox] section was from tox.ini. 

I usually code for python2/3 compatibility but this app used a python3 only library.  I just want the user to know that they need python3 for this utility. 

Thank you!

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On Jun 2, 2015, at 2:25 PM, Florian Bruhin <me at the-compiler.org> wrote:

> * Roy Wright <roy at wright.org> [2015-06-02 14:14:54 -0500]:
>> Howdy,
>> 
>> For my python3 apps I've been including the following to prevent them from being installed on python2:
>> 
>> import sys
>> if sys.version_info < (3, 3):
>>    print("appname requires python 3.3 or newer")
>>    exit(-1)
>> 
>> Now my system python is 2.7 (Ubuntu 14.04) so running tox will immediately fail even with:
>> 
>> [tox]
>> envlist = py33,py34
>> 
>> Removing the exit allows tox to run.
> 
> Where did you add that? I guess to setup.py?
> 
>> I'm just curious what is the best practice here?  Run tox from python3 virtualenv? Let the user beware? Depend on classifiers?
> 
> Being compatible with python3 only means you make life harder for
> contributors who are used to just being able to run 'tox'.
> 
> I have some similar check, but at runtime[1]. This means installing
> will work, but at least when running it the user gets a clear error.
> 
> Of course, this file must be python2 compatible, and everything
> imported/run before it at least not be a SyntaxError.
> 
> [1] https://github.com/The-Compiler/qutebrowser/blob/master/qutebrowser/misc/checkpyver.py
> 
> Florian
> 
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