Depending on a Python egg

[Kevin Golding]

I'm trying to add a dependency on another port which installs as an egg
and pretty much the only like dependency I can seem to find is on
devel/py-lxml - a few ports seem to require that so it defined:

PYLXML_EGG=     ${PORTNAME}-${PORTVERSION}-py${PYTHON_VER}${PYEASYINSTAL
L_OSARCH}.egg

And the other ports used:

RUN_DEPENDS=    ${PYTHON_SITELIBDIR}/${PYLXML_EGG}:${PORTSDIR}/devel/py-
lxml

.include <bsd.port.pre.mk>

PYLXML_EGG!=    ${MAKE} -f ${PORTSDIR}/devel/py-lxml/Makefile -V
PYLXML_EGG

.include <bsd.port.post.mk>

Now I say "defined" because just over a year ago py-lxml seemed to drop
that from it's Makefile.  The other ports still seem to be happy, but
now I can't see where the egg is defined.  Is there now some automagic
for such things?  I couldn't see anything obvious in bsd.python.mk so
I'm a little unsure the best practice for moving ahead with this.  Any
pointers greatly appreciated.

TIA,
Kevin