[Zope-dev] working with different requirements depending on python version

[Chris Withers]

Hi All,

While trying to debug another problem, I re-ran some Jenkins jobs for 
two of my packages, which promptly failed under Python 2.5:

http://jenkins.simplistix.co.uk/job/testfixtures-buildout/
http://jenkins.simplistix.co.uk/job/checker-buildout/

Now, the issue here is that zope.interface 4.0 and above no longer 
supports Python 2.5:

http://jenkins.simplistix.co.uk/job/checker-buildout/PYTHON=2.5,label=linux/15/console
http://pypi.python.org/pypi/zope.interface/4.0.0

That's fine, but I'd like the above projects to continue 2.5 support for 
the time being.

The simple solution would be to add a versions section to the buildout here:

https://github.com/Simplistix/checker/blob/master/buildout.cfg

...and pin the versions in the tox.ini here:

https://github.com/Simplistix/checker/blob/master/tox.ini

...however, that doesn't give the correct result. The version 
requirement is "use the latest version of all packages that work with 
the Python version under test" and the changes I've suggested would mean 
that on Python 2.6 and 2.7, the latest version of zope.interface 
wouldn't be used.

What makes this even more "interesting" is that zope.interface isn't a 
direct requirement of either of these projects, it's a dependency of a 
dependency in both cases.

How have other people solved this?

Chris

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