pybuild: how to get the build directory name

[Ole Streicher <olebole@debian.org>]

Hi,

one of my Python packages has a test script under debian/tests that I
want to run at build time. The problem is now how to get the name of the
actual build directory, which is needed to be put into the PYTHONPATH:

Up to now, I did the following in debian/rules:

test-python%:
        HOME=/tmp/ PYTHONPATH=$(CURDIR)/.pybuild/pythonX.Y_$*/build python$* debian/tests/pyraf-test.py

override_dh_auto_test: $(PYTHON2:%=test-python%) $(PYTHON3:%=test-python%)

This however does not work anymore, since the subdir under .pybuild is
now changed to cpython2_2.7_pyraf resp. cpython3_3.6_pyraf.

To be backward compatible, I would however not like to just follow this
change. How can I get the correct build dir here?

Best regards

Ole