[Distutils] bdist_wininst and dependencies with setuptools

["Martin v. Löwis"]

> By the way, is it possible, from the postinstall script, to know the
> Python instance used?

Sure: the python interpreter running the postinstall script *is* the
one being used. Look at sys.executable.

> There is one thing I'm not sure to understand about the bdist_wininst
> and bdist_msi commands: what is the reason why they don't simply execute
> `python setup.py install` in the background?

Primarily because this would users require to have Visual Studio
installed, plus potentially tons of header files and other build
dependencies (e.g. setuptools). Other reasons are:
- with a plain "setup.py install", uninstallation is not supported,
  but that is a feature of both bdist_wininst and bdist_msi
- you need to unpack the files first to run "setup.py install":
  where would you unpack them to?
- it's more efficient: installation runs faster.

Regards,
Martin