The current specification doesn't work at all, since there is no
architecture-specific build/lib.* directory. But the fallback to $PYTHONPATH
has the effect, if PYTHONPATH is empty, of adding the current directory to the
PYTHONPATH, and this causes the egg-info to be picked up by pkg_resources and
avoid a DistributionNotFound.

it isn't used, so why checkdepend on it?