[Distutils] whats the best way to depend on tools needed for setup.py/setup metadata

[Ronny Pfannschmidt]

Hi,

i'd like to support turning my guess version from hg metadata tool into
a setup dependency and thus kill the need to ship a python file.

Currently i just import it + call a function,
but that doesn't exactly work if the module is missing and a dependency.

Is there any way to turn it into some sort of plugin/extension that
automatically gets installed/used to get that metadata.

regards Ronny