[Distutils] Setting environment variables before building eggs w/ extensions using zc.buildout

[Martin Aspeli]

Nathan R. Yergler wrote:
> I had a problem come up today that I've run into before, and I'd like
> to figure out a way to prevent it from sucking my time down in the
> future.  Several apps we run at Creative Commons use lxml
> (http://codespeak.net/lxml) for XML, XSLT and XPath processing.  lxml
> builds on libxml2, and provides an element tree interface, plus
> additional capabilities.
> 
> We use zc.buildout to assemble our server-side applications, and that
> has generally been a huge sanity saver.  However, lxml can rob some of
> that sanity periodically.  If a system like one of our CentOS machines
> has an older version of libxml2 installed in /usr/lib, the extension
> building process will link against it without complaint.  That is,
> until you try to do something added in the later, recommended version
> of libxml2 like XSLT.  Once you scratch your head and remember what
> the problem is, you remember to export LD_LIBRARY_PATH=/usr/local/lib,
> and then re-run the buildout.
> 
> Does zc.buildout currently have any way to set an environment variable
> during it's run?  I didn't see anything at
> http://cheeseshop.python.org/pypi/zc.recipe.egg/, but I didn't know if
> there was something at the zc.buildout level (as opposed to the recipe
> level) that would do the trick.  The quick/dirty thing I'd do is
> export the appropriate value of LD_LIBRARY_PATH.  The perhaps more
> intelligent thing I'd do is use the cmmi recipe to build a version of
> libxml2 that I *know* has the features I need as part of the buildout,
> and then point LD_LIBRARY_PATH at that.
> 
> Or has anyone else run into a similar situation, who might have some insight?

I would be interested in something like this, specifically for building 
Deliverance.

Deliverance does have a buildout, that attempts to do this, but the 
deliverance buildout is pretty rough. Or rather, it's not easily 
re-usable, so if you want to build deliverance as part of a bigger 
project, it can be tricky.

I'd be interested in seeing and/or helping out with such a solution 
because I need to build deliverance as part of this project anyway, and 
I'd like an elegant way to do it.

See http://www.openplans.org/projects/deliverance and 
http://codespeak.net/svn/z3/deliverance/buildout/trunk/.

Martin