Backporting to Etch

[Andrew Malcolmson <andmalc@gmail.com>]

I'm trying to backport a minimal Python2.6 to Etch.  I've used
Pbuilder to create an Etch base and run:

pbuilder --build --basetgz /var/cache/pbuilder/base-etch.tgz
--distribution etch  python2.6_2.6.1-3.dsc

This runs and informs me that the following dependencies are missing:
tk8.5-dev, libffi-dev (>= 3.0.5), libgpm2, python-sphinx

How do I tell pbuilder that I don't need these features?

Is there a better way to do a backport?  I could manually compile the
source in an Etch chroot but I still wouldn't know which configure
options are needed to disable the above features ('configure --help'
doesn't show them)